Commit Graph

3 Commits

Author SHA1 Message Date
Geert Uytterhoeven
ec75039d55 gpio: aggregator: Use bitmap_parselist() for parsing GPIO offsets
Replace the custom code to parse GPIO offsets and/or GPIO offset ranges
by a call to bitmap_parselist(), and an iteration over the returned bit
mask.

This should have no impact on the format of the configuration parameters
written to the "new_device" virtual file in sysfs.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200701114212.8520-3-geert+renesas@glider.be
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
2020-07-07 14:30:27 +02:00
Geert Uytterhoeven
2073ea3ab1 gpio: aggregator: Drop pre-initialization in get_arg()
In get_arg(), the variable start is pre-initialized, but overwritten
again in the first statement.  Rework the assignment to not rely on
pre-initialization, to make the code easier to read.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200701114212.8520-2-geert+renesas@glider.be
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
2020-07-07 14:30:27 +02:00
Geert Uytterhoeven
828546e242 gpio: Add GPIO Aggregator
GPIO controllers are exported to userspace using /dev/gpiochip*
character devices.  Access control to these devices is provided by
standard UNIX file system permissions, on an all-or-nothing basis:
either a GPIO controller is accessible for a user, or it is not.
Currently no mechanism exists to control access to individual GPIOs.

Hence add a GPIO driver to aggregate existing GPIOs, and expose them as
a new gpiochip.

This supports the following use cases:
  - Aggregating GPIOs using Sysfs
    This is useful for implementing access control, and assigning a set
    of GPIOs to a specific user or virtual machine.
  - Generic GPIO Driver
    This is useful for industrial control, where it can provide
    userspace access to a simple GPIO-operated device described in DT,
    cfr. e.g. spidev for SPI-operated devices.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20200511145257.22970-5-geert+renesas@glider.be
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
2020-05-18 10:12:42 +02:00