On Thu, Jun 13, 2024 at 12:02 PM Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Jun 13, 2024 at 11:28:30AM +0200, Bartosz Golaszewski wrote: > > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > > > > The GPIO subsystem used to have a serious problem with undefined behavior > > and use-after-free bugs on hot-unplug of GPIO chips. This can be > > considered a corner-case by some as most GPIO controllers are enabled > > early in the boot process and live until the system goes down but most > > GPIO drivers do allow unbind over sysfs, many are loadable modules that > > can be (force) unloaded and there are also GPIO devices that can be > > dynamically detached, for instance CP2112 which is a USB GPIO expender. > > > > Bugs can be triggered both from user-space as well as by in-kernel users. > > We have the means of testing it from user-space via the character device > > but the issues manifest themselves differently in the kernel. > > > > This is a proposition of adding a new virtual driver - a configurable > > GPIO consumer that can be configured over configfs (similarly to > > gpio-sim) or described on the device-tree. > > > > This driver is aimed as a helper in spotting any regressions in > > hot-unplug handling in GPIOLIB. > > > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx> > > --- > > .../admin-guide/gpio/gpio-virtuser.rst | 176 ++ > > Documentation/admin-guide/gpio/index.rst | 1 + > > sysfs documentation needs to go in Documentation/ABI/ not in a random > .rst file where the tools that check this will not catch it. > This is a testing driver, not representing real hardware. Do we hold such modules to the same standard? > > MAINTAINERS | 8 + > > drivers/misc/Kconfig | 8 + > > drivers/misc/Makefile | 1 + > > drivers/misc/gpio-virtuser.c | 1790 +++++++++++++++++ > > Why not put this in drivers/gpio/? Why misc? > Because it's quite... well "misc". It's not a GPIO chip provider (drivers/gpio/ is for GPIO providers), it's only a GPIO consumer. It also has an interface that doesn't fit any particular subsystem. > > +Both attributes allow to read and set arrays of GPIO values. User must pass > > +exactly the number of values that the array contains in the form of a string > > +containing zeroes and ones representing inactive and active GPIO states > > +respectively. In this example: ``echo 11 > values``. > > sysfs is "one value per file", so why are there multiple values here? > > If you want to just use this for testing, and want to put whatever you > want in the files, just use debugfs, that's what it is there for, not > sysfs. > Debugfs doesn't allow me to attach attributes to a particular device which is what I want here. Bart > > +config GPIO_VIRTUSER > > + tristate "GPIO Virtual User Testing Module" > > + select CONFIGFS_FS > > + select IRQ_WORK > > + help > > + This enables the configurable, configfs-based virtual GPIO consumer > > + testing driver. > > + > > module name? > > And you need more documentation here, I have no idea what this means > when it shows up in a Kconfig help entry :( > > thanks, > > greg k-h
