gpiolib: cdev: fix uninitialised kfifo

If a line is requested with debounce, and that results in debouncing
in software, and the line is subsequently reconfigured to enable edge
detection then the allocation of the kfifo to contain edge events is
overlooked. This results in events being written to and read from an
uninitialised kfifo. Read events are returned to userspace.

Initialise the kfifo in the case where the software debounce is
already active.

Fixes: 65cff7046406 ("gpiolib: cdev: support setting debounce")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20240510065342.36191-1-warthog618@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: Fix use after free in lineinfo_changed_notify

The use-after-free issue occurs as follows: when the GPIO chip device file
is being closed by invoking gpio_chrdev_release(), watched_lines is freed
by bitmap_free(), but the unregistration of lineinfo_changed_nb notifier
chain failed due to waiting write rwsem. Additionally, one of the GPIO
chip's lines is also in the release process and holds the notifier chain's
read rwsem. Consequently, a race condition leads to the use-after-free of
watched_lines.

Here is the typical stack when issue happened:

[free]
gpio_chrdev_release()
--> bitmap_free(cdev->watched_lines) <-- freed
--> blocking_notifier_chain_unregister()
--> down_write(&nh->rwsem) <-- waiting rwsem
--> __down_write_common()
--> rwsem_down_write_slowpath()
--> schedule_preempt_disabled()
--> schedule()

[use]
st54spi_gpio_dev_release()
--> gpio_free()
--> gpiod_free()
--> gpiod_free_commit()
--> gpiod_line_state_notify()
--> blocking_notifier_call_chain()
--> down_read(&nh->rwsem); <-- held rwsem
--> notifier_call_chain()
--> lineinfo_changed_notify()
--> test_bit(xxxx, cdev->watched_lines) <-- use after free

The side effect of the use-after-free issue is that a GPIO line event is
being generated for userspace where it shouldn't. However, since the chrdev
is being closed, userspace won't have the chance to read that event anyway.

To fix the issue, call the bitmap_free() function after the unregistration
of lineinfo_changed_nb notifier chain.

Fixes: 51c1064e82e7 ("gpiolib: add new ioctl() for monitoring changes in line info")
Signed-off-by: Zhongqiu Han <quic_zhonhan@quicinc.com>
Link: https://lore.kernel.org/r/20240505141156.2944912-1-quic_zhonhan@quicinc.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: use a single SRCU struct for all GPIO descriptors

We used a per-descriptor SRCU struct in order to not impose a wait with
synchronize_srcu() for descriptor X on read-only operations of
descriptor Y. Now that we no longer call synchronize_srcu() on
descriptor label change but only when releasing descriptor resources, we
can use a single SRCU structure for all GPIO descriptors in a given chip.

Suggested-by: "Paul E. McKenney" <paulmck@kernel.org>
Acked-by: "Paul E. McKenney" <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20240507172414.28513-1-brgl@bgdev.pl
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpio: cdev: fix missed label sanitizing in debounce_setup()

When adding sanitization of the label, the path through
edge_detector_setup() that leads to debounce_setup() was overlooked.
A request taking this path does not allocate a new label and the
request label is freed twice when the request is released, resulting
in memory corruption.

Add label sanitization to debounce_setup().

Cc: stable@vger.kernel.org
Fixes: b34490879baa ("gpio: cdev: sanitize the label before requesting the interrupt")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
[Bartosz: rebased on top of the fix for empty GPIO labels]
Co-developed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpio: cdev: check for NULL labels when sanitizing them for irqs

We need to take into account that a line's consumer label may be NULL
and not try to kstrdup() it in that case but rather pass the NULL
pointer up the stack to the interrupt request function.

To that end: let make_irq_label() return NULL as a valid return value
and use ERR_PTR() instead to signal an allocation failure to callers.

Cc: stable@vger.kernel.org
Fixes: b34490879baa ("gpio: cdev: sanitize the label before requesting the interrupt")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/lkml/20240402093534.212283-1-naresh.kamboju@linaro.org/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>

gpio: cdev: sanitize the label before requesting the interrupt

When an interrupt is requested, a procfs directory is created under
"/proc/irq/<irqnum>/<label>" where <label> is the string passed to one of
the request_irq() variants.

What follows is that the string must not contain the "/" character or
the procfs mkdir operation will fail. We don't have such constraints for
GPIO consumer labels which are used verbatim as interrupt labels for
GPIO irqs. We must therefore sanitize the consumer string before
requesting the interrupt.

Let's replace all "/" with ":".

Cc: stable@vger.kernel.org
Reported-by: Stefan Wahren <wahrenst@gmx.net>
Closes: https://lore.kernel.org/linux-gpio/39fe95cb-aa83-4b8b-8cab-63947a726754@gmx.net/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpio: cdev: fix a NULL-pointer dereference with DEBUG enabled

We are actually passing the gc pointer to chip_dbg() so we have to
srcu_dereference() it.

Fixes: 8574b5b47610 ("gpio: cdev: use correct pointer accessors with SRCU")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Closes: https://lore.kernel.org/lkml/179caa10-5f86-4707-8bb0-fe1b316326d6@samsung.com/
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

gpio: cdev: use correct pointer accessors with SRCU

We never dereference the chip pointer in character device code so we can
use the lighter rcu_access_pointer() helper. This also makes lockep
happier as it no longer complains about suspicious rcu_dereference()
usage.

Fixes: d83cee3d2bb1 ("gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202402122234.d85cca9b-lkp@intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>

gpio: protect the pointer to gpio_chip in gpio_device with SRCU

Ensure we cannot crash if the GPIO device gets unregistered (and the
chip pointer set to NULL) during any of the API calls.

To that end: wait for all users of gdev->chip to exit their read-only
SRCU critical sections in gpiochip_remove().

For brevity: add a guard class which can be instantiated at the top of
every function requiring read-only access to the chip pointer and use it
in all API calls taking a GPIO descriptor as argument. In places where
we only deal with the GPIO device - use regular guard() helpers and
rcu_dereference() for chip access. Do the same in API calls taking a
const pointer to gpio_desc.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: cdev: don't access gdev->chip if it's not needed

The variable holding the number of GPIO lines is duplicated in GPIO
device so read it instead of unnecessarily dereferencing the chip
pointer.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: cdev: replace gpiochip_get_desc() with gpio_device_get_desc()

gpio_device_get_desc() is the safer alternative to gpiochip_get_desc().
As we don't really need to dereference the chip pointer to retrieve the
descriptors in character device code, let's use it.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: remove gpio_lock

The "multi-function" gpio_lock is pretty much useless with how it's used
in GPIOLIB currently. Because many GPIO API calls can be called from all
contexts but may also call into sleeping driver callbacks, there are
many places with utterly broken workarounds like yielding the lock to
call a possibly sleeping function and then re-acquiring it again without
taking into account that the protected state may have changed.

It was also used to protect several unrelated things: like individual
descriptors AND the GPIO device list. We now serialize access to these
two with SRCU and so can finally remove the spinlock.

There is of course the question of consistency of lockless access to
GPIO descriptors. Because we only support exclusive access to GPIOs
(officially anyway, I'm looking at you broken
GPIOD_FLAGS_BIT_NONEXCLUSIVE bit...) and the API contract with providers
does not guarantee serialization, it's enough to ensure we cannot
accidentally dereference an invalid pointer and that the state we present
to both users and providers remains consistent. To achieve that: read the
flags field atomically except for a few special cases. Read their current
value before executing callback code and use this value for any subsequent
logic. Modifying the flags depends on the particular use-case and can
differ. For instance: when requesting a GPIO, we need to set the
REQUESTED bit immediately so that the next user trying to request the
same line sees -EBUSY.

While at it: the allocations that used GFP_ATOMIC until this point can
now switch to GFP_KERNEL.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: protect the descriptor label with SRCU

In order to ensure that the label is not freed while it's being
accessed, let's protect it with SRCU and synchronize it everytime it's
changed.

Let's modify desc_set_label() to manage the memory used for the label as
it can only be freed once synchronize_srcu() returns.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: provide and use gpiod_get_label()

We will soon serialize access to the descriptor label using SRCU. The
write-side of the protection will require calling synchronize_srcu()
which must not be called from atomic context. We have two irq helpers:
gpiochip_lock_as_irq() and gpiochip_unlock_as_irq() that set the label
if the GPIO is not requested but is being used as interrupt. They are
called with a spinlock held from the interrupt subsystem.

They must not do it if we are to use SRCU so instead let's move the
special corner case to a dedicated getter.

First: let's implement and use the getter where it's applicable.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: cdev: remove leftover function pointer typedefs

The locking wrappers were replaces with lock guards. These typedefs are
no longer needed.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: cdev: replace locking wrappers for gpio_device with guards

Replace the wrapping functions that inhibit removal of the gpio chip
with equivalent guards.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: replace locking wrappers for config_mutex with guards

After the adoption of guard(), the locking wrappers that hold the
config_mutex for linereq_set_values() and linereq_set_config() no
longer add value, so combine them into the functions they wrap.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: allocate linereq using kvzalloc()

The size of struct linereq may exceed a page, so allocate space for
it using kvzalloc() instead of kzalloc() to handle the case where
memory is heavily fragmented and kzalloc() cannot find a sufficient
contiguous region.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: include overflow.h

struct_size() is used to calculate struct linereq size, so explicitly
include overflow.h.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: reduce locking in gpio_desc_to_lineinfo()

Reduce the time holding the gpio_lock by snapshotting the desc flags,
rather than testing them individually while holding the lock.

Accept that the calculation of the used field is inherently racy, and
only check the availability of the line from pinctrl if other checks
pass, so avoiding the check for lines that are otherwise in use.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: improve documentation of get/set values

Add documentation of the algorithm used to perform scatter/gather
of the requested lines and values in linereq_get_values() and
linereq_set_values_unlocked() to improve maintainability.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: fully adopt guard() and scoped_guard()

Use guard() or scoped_guard() for critical sections rather than
discrete lock/unlock pairs.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: relocate debounce_period_us from struct gpio_desc

Store the debounce period for a requested line locally, rather than in
the debounce_period_us field in the gpiolib struct gpio_desc.

Add a global tree of lines containing supplemental line information
to make the debounce period available to be reported by the
GPIO_V2_GET_LINEINFO_IOCTL and the line change notifier.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: cdev: add gpio_device locking wrapper around gpio_ioctl()

While the GPIO cdev gpio_ioctl() call is in progress, the kernel can
call gpiochip_remove() which will set gdev->chip to NULL, after which
any subsequent access will cause a crash.

gpio_ioctl() was overlooked by the previous fix to protect syscalls
(bdbbae241a04), so add protection for that.

Fixes: bdbbae241a04 ("gpiolib: protect the GPIO device against being dropped while in use by user-space")
Fixes: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines")
Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

treewide: rename pinctrl_gpio_can_use_line_new()

Now that pinctrl_gpio_can_use_line() is no longer used, let's drop the
'_new' suffix from its improved variant.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

gpio: cdev: use pinctrl_gpio_can_use_line_new()

Use the improved variant of pinctrl_gpio_can_use_line() which takes a
pointer to the gpio_chip and a controller-relative offset.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: annotate struct linereq with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct linereq.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: provide and use gpiod_line_state_notify()

Wrap the calls to blocking_notifier_call_chain() for the line state
notifier with a helper that allows us to use fewer lines of code and
simpler syntax.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

gpio: cdev: wake up lineevent poll() on device unbind

Add a notifier block to the lineevent_state structure and register it
with the gpio_device's device notifier. Upon reception of an event, wake
up the wait queue so that the user-space be forced out of poll() and
need to go into a new system call which will then fail due to the chip
being gone.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpio: cdev: wake up linereq poll() on device unbind

Add a notifier block to the linereq structure and register it with the
gpio_device's device notifier. Upon reception of an event, wake up the
wait queue so that the user-space be forced out of poll() and need to go
into a new system call which will then fail due to the chip being gone.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpio: cdev: wake up chardev poll() on device unbind

Add a notifier block to the gpio_chardev_data structure and register it
with the gpio_device's device notifier. Upon reception of an event, wake
up the wait queue so that the user-space be forced out of poll() and need
to go into a new system call which will then fail due to the chip being
gone.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: add a second blocking notifier to struct gpio_device

Add a new blocking notifier to struct gpio_device and use it to notify
subscribers about the GPIO device being unregistered from the device
model.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpio: cdev: open-code to_gpio_chardev_data()

This function is a wrapper around container_of(). It's used only once and
we will have a second notifier soon, so instead of having two flavors of
this helper, let's just open-code where needed.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: rename the gpio_device notifier

Change the generic "notifier" name to "line_state_notifier" in order to
reflect its purpose in preparation for adding a second notifier which
will be used to notify wait queues about device unregistering.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: Introduce gpio_device_get() and gpio_device_put()

Introduce gpio_device_get() and gpio_device_put() helpers
and convert existing users.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiolib: protect the GPIO device against being dropped while in use by user-space

While any of the GPIO cdev syscalls is in progress, the kernel can call
gpiochip_remove() (for instance, when a USB GPIO expander is disconnected)
which will set gdev->chip to NULL after which any subsequent access will
cause a crash.

To avoid that: use an RW-semaphore in which the syscalls take it for
reading (so that we don't needlessly prohibit the user-space from calling
syscalls simultaneously) while gpiochip_remove() takes it for writing so
that it can only happen once all syscalls return.

Fixes: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines")
Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL")
Fixes: 7b8e00d98168 ("gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
[Nick: fixed a build failure with CDEV_V1 disabled]
Co-authored-by: Nick Hainke <vincent@systemli.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: fix NULL-pointer dereferences

There are several places where we can crash the kernel by requesting
lines, unbinding the GPIO device, then calling any of the system calls
relevant to the GPIO character device's annonymous file descriptors:
ioctl(), read(), poll().

While I observed it with the GPIO simulator, it will also happen for any
of the GPIO devices that can be hot-unplugged - for instance any HID GPIO
expander (e.g. CP2112).

This affects both v1 and v2 uAPI.

This fixes it partially by checking if gdev->chip is not NULL but it
doesn't entirely remedy the situation as we still have a race condition
in which another thread can remove the device after the check.

Fixes: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines")
Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL")
Fixes: 7b8e00d98168 ("gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: Fix typo in kernel doc for struct line

When eflags has been renamed to the edflags, the kernel doc change were
missed. Update kernel doc accordingly.

Fixes: b1a92e94560d ("gpiolib: cdev: consolidate edge detector configuration flags")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: cdev: Add missing header(s)

Do not imply that some of the generic headers may be always included.
Instead, include explicitly what we are direct user of.

While at it, sort headers alphabetically.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Rewiewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: cdev: add fdinfo output for line request file descriptors

Add fdinfo output for file descriptors created for user-space line
requests in GPIO uAPI v2. The fdinfo file now contains the name of the
GPIO chip that is the "parent" of the request as well as offsets of
the lines requested. This allows user-space to parse the /proc/$PID/fdinfo
entries and deduce the PID of the process that requested a specific line.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Kent Gibson <warthog618@gmail.com>

gpiolib: cdev: Set lineevent_state::irq after IRQ register successfully

When running gpio test on nxp-ls1028 platform with below command
gpiomon --num-events=3 --rising-edge gpiochip1 25
There will be a warning trace as below:
Call trace:
free_irq+0x204/0x360
lineevent_free+0x64/0x70
gpio_ioctl+0x598/0x6a0
__arm64_sys_ioctl+0xb4/0x100
invoke_syscall+0x5c/0x130
......
el0t_64_sync+0x1a0/0x1a4
The reason of this issue is that calling request_threaded_irq()
function failed, and then lineevent_free() is invoked to release
the resource. Since the lineevent_state::irq was already set, so
the subsequent invocation of free_irq() would trigger the above
warning call trace. To fix this issue, set the lineevent_state::irq
after the IRQ register successfully.

Fixes: 468242724143 ("gpiolib: cdev: refactor lineevent cleanup into lineevent_free")
Cc: stable@vger.kernel.org
Signed-off-by: Meng Li <Meng.Li@windriver.com>
Reviewed-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: compile out HTE unless CONFIG_HTE selected

The majority of builds do not include HTE, so compile out hte
functionality unless CONFIG_HTE is selected.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: consolidate edge detector configuration flags

Combine the polarity_change flag, struct line eflags, and hte enable
flag into a single flag variable.

The combination of these flags describes the configuration state
of the edge detector, so formalize and clarify that by combining
them into a single variable, edflags, in struct line.

The edflags is a subset of the GPIO_V2_LINE_FLAGsb relevant to
the edge detector, and is also a superset of the eflags it replaces.
The eflags name is still used to describe the subset of edflags
corresponding to the rising/falling edge flags where edflags is
masked down to that subset.

This consolidation reduces the number of variables being passed,
simplifies state comparisons, and provides a more extensible
foundation should additional edge sources be integrated in the
future.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: simplify line event identification

Reorganise line event identification code to reduce code duplication,
and replace if-else initializers with a helper function to improve
readability.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: replace if-else chains with switches

Improve readability by replacing if-else chains with switch
statements.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: simplify parameter in call to hte_edge_setup

Improve readability by using the GPIO_V2_LINE_FLAG_EDGE_BOTH instead
of combining the rising and falling edge flags.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Dipen Patel <dipenp@nvidia.com>
Tested-by: Dipen Patel <dipenp@nvidia.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: simplify linereq_free

The edge detector is only ever started after the line desc has been
determined, so move edge_detector_stop() inside the line desc check,
and merge the two checked regions into one.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Dipen Patel <dipenp@nvidia.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: Fix kernel doc for struct line

Kernel doc validator is not happy:
gpiolib-cdev.c:487: warning: Function parameter or member 'hdesc' not described in 'line'
gpiolib-cdev.c:487: warning: Function parameter or member 'raw_level' not described in 'line'
gpiolib-cdev.c:487: warning: Function parameter or member 'total_discard_seq' not described in 'line'
gpiolib-cdev.c:487: warning: Function parameter or member 'last_seqno' not described in 'line'

Describe above mentioned parameters.

Fixes: 2068339a6c35 ("gpiolib: cdev: Add hardware timestamp clock type")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Dipen Patel <dipenp@nvidia.com>
Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Thierry Reding <treding@nvidia.com>

gpiolib: cdev: fix null pointer dereference in linereq_free()

Fix a kernel NULL pointer dereference reported by gpio kselftests.

linereq_free() can be called as part of the cleanup of a failed request,
at which time the desc for a line may not have been determined, so it
is unsafe to dereference without a check.

Add a check prior to dereferencing the line desc.

Fixes: 2068339a6c35 ("gpiolib: cdev: Add hardware timestamp clock type")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: Add hardware timestamp clock type

This patch adds new clock type for the GPIO controller which can
timestamp gpio lines in using hardware means. To expose such
functionalities to the userspace, code has been added where
during line create or set config API calls, it checks for new
clock type and if requested, calls HTE API. During line change
event, the HTE subsystem pushes timestamp data to userspace
through gpiolib-cdev.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

gpiolib: Get rid of redundant 'else'

In the snippets like the following

if (...)
return / goto / break / continue ...;
else
...

the 'else' is redundant. Get rid of it. In case of IOCTLs use
switch-case pattern that seems the usual in such cases.

While at it, clarify necessity of else in gpiod_direction_output()
by attaching else if to the closing curly brace on a previous line.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: Never return internal error codes to user space

Currently it's possible that character device interface may return
the error codes which are not supposed to be seen by user space.
In this case it's EPROBE_DEFER.

Wrap it to return -ENODEV instead as sysfs does.

Fixes: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines")
Fixes: 61f922db7221 ("gpio: userspace ABI for reading GPIO line events")
Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
Reported-by: Suresh Balakrishnan <suresh.balakrishnan@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpiolib: cdev: zero padding during conversion to gpioline_info_changed

When userspace requests a GPIO v1 line info changed event,
lineinfo_watch_read() populates and returns the gpioline_info_changed
structure. It contains 5 words of padding at the end which are not
initialized before being returned to userspace.

Zero the structure in gpio_v2_line_info_change_to_v1() before populating
its contents.

Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Signed-off-by: Gabriel Knezek <gabeknez@linux.microsoft.com>
Reviewed-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: clear debounce period if line set to output

When set_config changes a line from input to output debounce is
implicitly disabled, as debounce makes no sense for outputs, but the
debounce period is not being cleared and is still reported in the
line info.

So clear the debounce period when the debouncer is stopped in
edge_detector_stop().

Fixes: 65cff7046406 ("gpiolib: cdev: support setting debounce")
Cc: stable@vger.kernel.org
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: fix frame size warning in gpio_ioctl()

The kernel test robot reports the following warning in [1]:

drivers/gpio/gpiolib-cdev.c: In function 'gpio_ioctl':
>>drivers/gpio/gpiolib-cdev.c:1437:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]

Refactor gpio_ioctl() to handle each ioctl in its own helper function
and so reduce the variables stored on the stack to those explicitly
required to service the ioctl at hand.

The lineinfo_get_v1() helper handles both the GPIO_GET_LINEINFO_IOCTL
and GPIO_GET_LINEINFO_WATCH_IOCTL, as per the corresponding v2
implementation - lineinfo_get().

[1] https://lore.kernel.org/lkml/202012270910.VW3qc1ER-lkp@intel.com/

Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: Flag invalid GPIOs as used

When reporting the state of a GPIO to userspace, we never check
for the actual validity of the line, meaning we report invalid
lines as being usable. A subsequent request will fail though,
which is an inconsistent behaviour from a userspace perspective.

Instead, let's check for the validity of the line and report it
as used if it is invalid. This allows a tool such as gpioinfo
to report something sensible:

gpiochip3 - 4 lines:
line 0: unnamed unused input active-high
line 1: unnamed kernel input active-high [used]
line 2: unnamed kernel input active-high [used]
line 3: unnamed unused input active-high

In this example, lines 1 and 2 are invalid, and cannot be used by
userspace.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201204164739.781812-2-maz@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: allow edge event timestamps to be configured as REALTIME

Using CLOCK_REALTIME as the source for event timestamps is crucial for
some specific applications, particularly those requiring timetamps
relative to a PTP clock, so provide an option to switch the event
timestamp source from the default CLOCK_MONOTONIC to CLOCK_REALTIME.

Note that CLOCK_REALTIME was the default source clock for GPIO until
Linux 5.7 when it was changed to CLOCK_MONOTONIC due to issues with the
shifting of the realtime clock.
Providing this option maintains the CLOCK_MONOTONIC as the default,
while also providing a path forward for those dependent on the pre-5.7
behaviour.

Suggested-by: Jack Winch <sunt.un.morcov@gmail.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20201014231158.34117-2-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: add GPIO_V2_LINE_FLAG_EDGE_BOTH and use it in edge_irq_thread()

Add GPIO_V2_LINE_FLAG_EDGE_BOTH macro and use it in edge_irq_thread() to
improve readability of edge handling cases.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: Switch to use compat_need_64bit_alignment_fixup() helper

Use the new compat_need_64bit_alignment_fixup() helper to avoid
ugly ifdeffery in IOCTL compatibility code.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Kent Gibson <warthog618@gmail.com>
Depends-on: 527c412519eb ("compat: add a compat_need_64bit_alignment_fixup() helper")
Link: https://lore.kernel.org/r/20201014103315.82662-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: document that line eflags are shared

The line.eflags field is shared so document this fact and highlight it
throughout using READ_ONCE() and WRITE_ONCE() accessors.

Also use a local copy of the eflags in edge_irq_thread() to ensure
consistent control flow even if eflags changes. This is only a defensive
measure as edge_irq_thread() is currently disabled when the eflags are
changed.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: switch from kstrdup() to kstrndup()

Use kstrndup() to copy line labels from the userspace provided char
array, rather than ensuring the char array contains a null terminator
and using kstrdup().

Note that the length provided to kstrndup() still assumes that the char
array does contain a null terminator, so the maximum string length is one
less than the array. This is consistent with the previous behaviour.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20201005070246.20927-1-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: Disable compat ->read() code in UML case

It appears that UML (arch/um) has no compat.h header defined and hence
can't compile a recently provided piece of code in GPIO library.

Disable compat ->read() code in UML case to avoid compilation errors.

While at it, use pattern which is already being used in the kernel elsewhere.

Fixes: 5ad284ab3a01 ("gpiolib: Fix line event handling in syscall compatible mode")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20201005131044.87276-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

gpiolib: cdev: support setting debounce

Add support for setting debounce on a line via the GPIO uAPI.
Where debounce is not supported by hardware, a software debounce is
provided.

The implementation of the software debouncer waits for the line to be
stable for the debounce period before determining if a level change,
and a corresponding edge event, has occurred. This provides maximum
protection against glitches, but also introduces a debounce_period
latency to edge events.

The software debouncer is integrated with the edge detection as it
utilises the line interrupt, and integration is simpler than getting
the two to interwork. Where software debounce AND edge detection is
required, the debouncer provides both.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL

Add support for the GPIO_V2_LINE_SET_VALUES_IOCTL.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL

Add support for GPIO_V2_LINE_SET_CONFIG_IOCTL, the uAPI v2
line set config ioctl.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: support edge detection for uAPI v2

Add support for edge detection to lines requested using
GPIO_V2_GET_LINE_IOCTL.

The edge_detector implementation is based on the v1 lineevent
implementation. Unlike the v1 implementation, an overflow of the event
buffer results in discarding older events, rather than the most
recent, so the final event in a burst will correspond to the current
state of the line.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL

Add support for GPIO_V2_GET_LINEINFO_IOCTL and
GPIO_V2_GET_LINEINFO_WATCH_IOCTL.

The core of this change is the event kfifo switching to contain
struct gpioline_info_changed_v2, instead of v1 as v2 is richer.

The two uAPI versions are mostly independent - other than where they both
provide line info changes via reads on the chip fd. As the info change
structs differ between v1 and v2, the infowatch implementation tracks which
version of the infowatch ioctl, either GPIO_GET_LINEINFO_WATCH_IOCTL or
GPIO_V2_GET_LINEINFO_WATCH_IOCTL, initiates the initial watch and returns
the corresponding info change struct to the read. The version supported
on that fd locks to that version on the first watch request, so subsequent
watches from that process must use the same uAPI version.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL

Add support for requesting lines using the GPIO_V2_GET_LINE_IOCTL, and
returning their current values using GPIO_V2_LINE_GET_VALUES_IOCTL.

The struct linereq implementation is based on the v1 struct linehandle
implementation.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: replace strncpy() with strscpy()

Replace usage of strncpy() with strscpy() to remove -Wstringop-truncation
warnings.

The structures being populated are zeroed, to prevent stack leakage as
they are returned to userspace, so strscpy() performs the equivalent
function without the warnings.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: gpio_desc_to_lineinfo() should set info offset

Set the value of the line info offset in gpio_desc_to_lineinfo(), rather
than relying on it being passed in the info. This makes the function
behave as you would expect from the name - it generates the line info
corresponding to a given GPIO desc.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: Fix line event handling in syscall compatible mode

The introduced line event handling ABI in the commit

61f922db7221 ("gpio: userspace ABI for reading GPIO line events")

missed the fact that 64-bit kernel may serve for 32-bit applications.
In such case the very first check in the lineevent_read() will fail
due to alignment differences.

To workaround this introduce lineevent_get_size() helper which returns actual
size of the structure in user space.

Fixes: 61f922db7221 ("gpio: userspace ABI for reading GPIO line events")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: refactor lineevent cleanup into lineevent_free

Consolidate the cleanup of lineevents, currently duplicated in
lineevent_create and lineevent_release, into a helper function
lineevent_free.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: refactor linehandle cleanup into linehandle_free

Consolidate the cleanup of linehandles, currently duplicated in
linehandle_create and linehandle_release, into a helper function
linehandle_free.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: remove recalculation of offset

Remove recalculation of offset from desc, where desc itself was calculated
from offset.

There is no benefit from the desc -> hwgpio conversion in this context.
The only implicit benefit of the offset -> desc -> hwgpio is
the range check in the offset -> desc, but where desc is required you
still get that, and where desc isn't required it is simpler to perform
the range check directly.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH

Merge separate usage of test_bit/set_bit into test_and_set_bit to remove
the possibility of a race between the test and set.

Similarly test_bit and clear_bit.

In the existing code it is possible for two threads to race past the
test_bit and then set or clear the watch bit, and neither return EBUSY.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: rename priv to cdev

Rename priv to cdev to improve readability.

The name "priv" indicates that the object is pointed to by
file->private_data, not what the object is actually is.
As it is always used to point to a struct gpio_chardev_data, renaming
it to cdev is more appropriate.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: use blocking notifier call chain instead of atomic

Replace usage of atomic_notifier_call_chain with
blocking_notifier_call_chain as the notifier function,
lineinfo_changed_notify, calls gpio_desc_to_lineinfo,
which calls pinctrl_gpio_can_use_line, which can sleep.

The chain isn't being called from an atomic context so the
the blocking notifier is a suitable substitute.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: remove pointless decrement of i

Remove pointless decrement of variable, and associated comment.

While i is used subsequently, it is re-initialized so this decrement
serves no purpose.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: rename numdescs to num_descs

Rename numdescs to num_descs to be more consistent with the naming of
other counters and improve readability.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: rename 'filep' and 'filp' to 'file' to be consistent with other use

Rename 'filep' and 'filp' to 'file' to be consistent with other use
and improve readability.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: refactor gpiohandle_flags_to_desc_flags

Refactor the mapping from handle flags to desc flags into a helper
function.

The assign_bit is overkill where it is replacing the set_bit cases, as is
rechecking bits known to be clear in some circumstances, but the DRY
simplification more than makes up for any performance degradation,
especially as this is not a hot path.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: minor indentation fixes

Make indentation consistent with other use to improve readability.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: cdev: sort includes

Sort the includes of gpiolib-cdev.c to make it easier to identify if a
module is included and to avoid duplication.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

gpiolib: split character device into gpiolib-cdev

Split the cdev specific functionality out of gpiolib.c and into
gpiolib-cdev.c. This improves the readability and maintainability of both
the cdev and core gpiolib code.

Suggested-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20200616093615.5167-1-warthog618@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>