Hi,
On Fri, Aug 14, 2015 at 04:10:57PM +0200, Markus Pargmann wrote:
> Changes in v3:
> As discussed in the v2 thread, we are using the already existing gpiochip names
> now. To avoid races between kernel and userspace, the setup of gpio names in
> the gpio descriptors has to happen right before the gpiochip is added for use
> and after the gpio descriptors are available. Unfortunately this is exactly in
> the function gpiochip_add().
>
> So we can't use a a function as proposed in the discussion like
> gpiochip_set_names(), as this function would only be possible after we executed
> gpiochip_add(). Before that point the gpio descriptors are not available. But
> this can potentially lead to races between userspace and the gpio chip.
>
> That is the reason why I left the names array in the gpioscript. But this array
> is now only used to initialize the GPIO descriptors. The named sysfs
> directories are now created using the name stored in the gpio descriptor.
>
> As the name is now directly represented through the sysfs directory name, I am
> not sure if it makes sense to keep the patch which adds a 'name' property to
> the sysfs GPIO directories. For the moment it is still in this series.
Any feedback on this series?
Thanks,
Markus
>
> Other changes in v3:
> - Renamed generic of_parse_gpio() to of_parse_own_gpio()
> - Replaced pr_warn with dev_warn as the device is available in the parsing code
> in gpiolib-of
> - Introduced name collision checks when adding the names from gpiochip->names
> to the gpio descriptors
> - Added documentation about /sys/class/gpio/<GPIO>/name
> - Added check for DT in case the GPIO already has a name. This may happen as
> there are different ways to set a name, through 'line-name' property and
> node name
>
> Best Regards,
>
> Markus
>
>
> Changes in v2:
> - Removed patch 'gpiolib: Fix possible use of wrong name'
> - Removed discussed patch 'gpio: Allow hogged gpios to be requested' from this
> series
> - Fixed show gpio name patch (locks, (null) printing, and getting the descriptor)
> - Merged gpio name patch into gpio_name_to_desc() patch
>
> Description from v1:
>
> This is a proposal to add GPIO names to the kernel based on devicetree
> descriptions.
>
> This series adds GPIO name support. Until now it is only possible to use names
> for already requested GPIOs (for example what they are used for). It is not
> possible to identify GPIOs by a name although most of them have a name for
> example in the schematics of the board. This makes it difficult to identify
> a specific GPIO from userspace.
>
> As the GPIO name information is a hardware description this series uses the
> devicetree bindings introduced by the GPIO hogging mechanism, specifically
> 'line-name', to identify GPIOs. The sysfs 'export' file is changed to accept
> names as fallback. The gpio numbers still have a higher priority to ensure
> backwards compatibility.
>
> Exported GPIOs are still using their number as directory name (gpio<ID>). But the
> directories now contain a 'name' file which is '' for non-existent names and
> the name otherwise.
>
> This series can be used to have an easy name mapping for udev with a quite
> simple rule similar to this:
> SUBSYSTEM=="gpio", KERNEL=="gpio*", ATTR{name}!="(null)", ACTION=="add", \
> PROGRAM+="/bin/sh -c 'mkdir -p /dev/gpios; rm -f /dev/gpios/$attr{name}; ln -s /sys%p/ /dev/gpios/$attr{name}"
> With this rule udev adds a link for each exported GPIO with a name into
> /dev/gpios/. This way it is not necessary to know the number of a GPIO to use
> it.
>
>
> Markus Pargmann (9):
> gpiolib-of: Rename gpio_hog functions to be generic
> gpio: Introduce gpio descriptor 'name'
> gpiolib: Use GPIO name from names array for gpio descriptor
> gpio-sysfs: Use gpio descriptor name instead of gpiochip names array
> gpiolib: Add gpio name information to /sys/kernel/debug/gpio
> gpiolib-sysfs: Show gpio-name in /sys/class/gpio/gpio*/name
> gpiolib-sysfs: Add gpio name parsing for sysfs export
> gpiolib-of: Reuse 'line-name' from DT as gpio descriptor name
> gpiolib-of: Use dev_warn instead of pr_warn
>
> Documentation/ABI/testing/sysfs-gpio | 1 +
> drivers/gpio/gpiolib-of.c | 50 +++++++++++++---------
> drivers/gpio/gpiolib-sysfs.c | 67 +++++++++++++++++++++---------
> drivers/gpio/gpiolib.c | 80 ++++++++++++++++++++++++++++++++++--
> drivers/gpio/gpiolib.h | 3 ++
> include/linux/gpio/consumer.h | 7 ++++
> 6 files changed, 166 insertions(+), 42 deletions(-)
>
> --
> 2.4.6
>
>
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