Re: [PATCH v3 00/10] gpio: sysfs: add a per-chip export/unexport attribute pair

[Andy Shevchenko]

On Mon, Jun 30, 2025 at 02:37:07PM +0200, Bartosz Golaszewski wrote:
> Following our discussion[1], here's a proposal for extending the sysfs
> interface with attributes not referring to GPIO lines by their global
> numbers in a backward compatible way.
> 
> Long story short: there is now a new class device for each GPIO chip.
> It's called chipX where X is the ID of the device as per the driver
> model and it lives next to the old gpiochipABC where ABC is the GPIO
> base. Each new chip class device has a pair of export/unexport
> attributes which work similarly to the global ones under /sys/class/gpio
> but take hardware offsets within the chip as input, instead of the
> global numbers. Finally, each exported line appears at the same time as
> the global /sys/class/gpio/gpioABC as well as per-chip
> /sys/class/gpio/chipX/gpioY sysfs group.
> 
> The series contains the implementation of a parallel GPIO chip entry not
> containing the base GPIO number in the name and the corresponding sysfs
> attribute group for each exported line that lives under the new chip
> class device as well as a way to allow to compile out the legacy parts
> leaving only the new elements of the sysfs ABI.
> 
> This series passes the compatibility tests I wrote while working on the
> user-space compatibility layer for sysfs[2].

It seems I never expressed my overall opinion about this. I think the poking
sysfs and making it working with a new schema won't solve the issues that
character device was developed to target. If so, doing this just brings yet
another broken interface. I would be happy to be mistaken!

If I am mistaken, I would like to see a summary here that explains that clearly
that the new sysfs approach does not inherit design flaws of the original
implementation.

> [1] https://lore.kernel.org/all/CAMRc=McUCeZcU6co1aN54rTudo+JfPjjForu4iKQ5npwXk6GXA@xxxxxxxxxxxxxx/
> [2] https://github.com/brgl/gpio-sysfs-compat-tests

-- 
With Best Regards,
Andy Shevchenko