[SRU][K][J, hwe-5.17, oem-5.17, starfive-5.17, allwinner-5.17][PATCH 0/1] Enable CONFIG_GPIO_CDEV_V1

[Emil Renner Berthing]

[Impact]

 * The libgpiod2 library and gpiod tools shipped in Jammy don't work.

 * These tools are meant to replace the old sysfs interface and be
   a better and more efficient way to manipulate GPIOs from userspace.
   Unfortunately the latest release is still using v1 of the character
   device kernel API which is not enabled in Ubuntu kernels.

 * This is Kent Gibsons reply on the linux-gpio mailing list:

On Tue, Jul 12, 2022 at 09:48:45AM +0200, Alexandre Ghiti wrote:
> Hi,
>
> Ubuntu kernels do not enable GPIO_CDEV_V1 as it is deprecated, but the
> libgpiod package that we ship is still based on the latest version
> 1.6.3 which does not implement the API v2. So I'd like to update
> libgpiod, do you have any recommendations about what branch/sha1 I
> should use? Do you plan to make a release that implements the API v2?
>

Firstly, libgpiod is Bart's library so he is the authority, but this
is my understanding...

TLDR: You should keep GPIO_CDEV_V1 enabled.

v1 is deprecated from a development perspective, so all new feature
development will occur on v2, and new applications should target v2.
Existing apps targetting v1, be that directly or via libgpiod v1.6.3,
will require GPIO_CDEV_V1 until they migrate to v2.
The mainline kernel will continue to support v1 while userspace
transitions.

libgpiod v2 is in active development, and should reach its first release
shortly.
Note that it is NOT a plugin replacement for v1. It has a different API,
for similar reasons to why we had to switch in the kernel, so apps will
need to be actively migrated.

I wouldn't suggest making any effort to package libgpiod v2 until Bart
makes an official release.

Cheers,
Kent.

[Test Plan]

 * Run gpioinfo on a machine with exposed GPIOs and check that it lists
   the GPIOs and doesn't error with

   gpioinfo: error creating line iterator: Invalid argument

[Where problems could occur]

 * There may be code and scripts that hasn't been tested with a working
   libgpiod2/gpiod tools and uncover latent bugs.

Emil Renner Berthing (1):
  UBUNTU: [Config] Enable CONFIG_GPIO_CDEV_V1

 debian.master/config/annotations          | 4 +++-
 debian.master/config/config.common.ubuntu | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

-- 
2.36.1