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gpio: TODO: remove the item about the new debugfs interface

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The consensus among core GPIO stakeholders seems to be that a new
debugfs interface will only increase maintenance burden and will fail
to attract users that care about long-term stability of the ABI[1].
Let's not go this way and not add a fourth user-facing interface to the
GPIO subsystem.

[1] https://lore.kernel.org/all/9d3f1ca4-d865-45af-9032-c38cacc7fe93@pengutronix.de/

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250321-gpio-todo-updates-v1-1-7b38f07110ee@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Bartosz Golaszewski 2025-03-21 16:49:33 +01:00
parent 2eb5dc9a4b
commit 0c6dcc4948
1 changed files with 0 additions and 36 deletions
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drivers/gpio/TODO
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@ -156,42 +156,6 @@ multiplexing, pin configuration, GPIO, etc selectable options in one
and the same pin control and GPIO subsystem.
Debugfs in place of sysfs
The old sysfs code that enables simple uses of GPIOs from the
command line is still popular despite the existance of the proper
character device. The reason is that it is simple to use on
root filesystems where you only have a minimal set of tools such
as "cat", "echo" etc.
The old sysfs still need to be strongly deprecated and removed
as it relies on the global GPIO numberspace that assume a strict
order of global GPIO numbers that do not change between boots
and is independent of probe order.
To solve this and provide an ABI that people can use for hacks
and development, implement a debugfs interface to manipulate
GPIO lines that can do everything that sysfs can do today: one
directory per gpiochip and one file entry per line:
/sys/kernel/debug/gpiochip/gpiochip0
/sys/kernel/debug/gpiochip/gpiochip0/gpio0
/sys/kernel/debug/gpiochip/gpiochip0/gpio1
/sys/kernel/debug/gpiochip/gpiochip0/gpio2
/sys/kernel/debug/gpiochip/gpiochip0/gpio3
...
/sys/kernel/debug/gpiochip/gpiochip1
/sys/kernel/debug/gpiochip/gpiochip1/gpio0
/sys/kernel/debug/gpiochip/gpiochip1/gpio1
...
The exact files and design of the debugfs interface can be
discussed but the idea is to provide a low-level access point
for debugging and hacking and to expose all lines without the
need of any exporting. Also provide ample ammunition to shoot
oneself in the foot, because this is debugfs after all.
Moving over to immutable irq_chip structures
Most of the gpio chips implementing interrupt support rely on gpiolib