Now that jammy's out (which still includes CONFIG_GPIO_SYSFS), let's at
least consider this for kinetic. I would suggest it would sensible to at
least try this in an interim release prior to the next LTS. There will
undoubtedly be things that break, but it's probably better to be aware
of how much breakage potential there is around this (and what it would
take to encourage users over to libgpiod, or if that's practical in all
cases).
I'll add linux-raspi to the target list as that's probably the kernel
flavour that this will impact most and target to kinetic.
** Also affects: linux-raspi (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Kinetic)
Importance: Undecided
Status: Confirmed
** Also affects: linux-raspi (Ubuntu Kinetic)
Importance: Undecided
Status: New
** Tags added: rls-kk-incoming
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https://bugs.launchpad.net/bugs/1918583
Title:
Switch to libgpiod and disable CONFIG_GPIO_SYSFS
Status in linux package in Ubuntu:
Confirmed
Status in linux-raspi package in Ubuntu:
New
Status in linux source package in Kinetic:
Confirmed
Status in linux-raspi source package in Kinetic:
New
Bug description:
Ubuntu kernels are built with CONFIG_GPIO_SYSFS=y after
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1342153
debian.master/config/config.common.ubuntu: CONFIG_GPIO_SYSFS=y
However, this interface got deprecated for removal:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a0910d72afc69b25703f7be9bf7d13f18937a478
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fe95046e960b4b76e73dc1486955d93f47276134
"This marks the (optional) sysfs GPIO ABI as obsolete and schedules it for
removal in 2020."
https://www.kernel.org/doc/Documentation/gpio/sysfs.txt
"THIS ABI IS DEPRECATED, THE ABI DOCUMENTATION HAS BEEN MOVED TO
Documentation/ABI/obsolete/sysfs-gpio AND NEW USERSPACE CONSUMERS
ARE SUPPOSED TO USE THE CHARACTER DEVICE ABI. THIS OLD SYSFS ABI WILL
NOT BE DEVELOPED (NO NEW FEATURES), IT WILL JUST BE MAINTAINED."
libgpiod and the use of a character file-based interface is a
replacement to the sysfs interface:
https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/
Those two interfaces cannot be used interchangeably and working via libgpiod
is not possible when the sysfs interface is used:
sudo gpioget gpiochip0 12
gpioget: error reading GPIO values: Device or resource busy
sudo gpioinfo | grep 12
line 12: "GPIO12" "sysfs" input active-high [used]
It would be good to switch to a newer interface since the old one does not
get new features and there is no way to switch to libgpiod besides recompiling
the kernel with "CONFIG_GPIO_SYSFS=n"
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