[PATCH v6 1/4] drm: Introduce device wedged event

[Simona Vetter]

On Wed, Sep 25, 2024 at 06:04:43AM +0300, Raag Jadav wrote:
> On Tue, Sep 24, 2024 at 01:23:13PM +0200, Simona Vetter wrote:
> > On Mon, Sep 23, 2024 at 09:28:23AM +0530, Raag Jadav wrote:
> > > Introduce device wedged event, which will notify userspace of wedged
> > > (hanged/unusable) state of the DRM device through a uevent. This is
> > > useful especially in cases where the device is no longer operating as
> > > expected and has become unrecoverable from driver context.
> > > 
> > > Purpose of this implementation is to provide drivers a way to recover
> > > through userspace intervention. Different drivers may have different
> > > ideas of a "wedged device" depending on their hardware implementation,
> > > and hence the vendor agnostic nature of the event. It is up to the drivers
> > > to decide when they see the need for recovery and how they want to recover
> > > from the available methods.
> > > 
> > > Current implementation defines three recovery methods, out of which,
> > > drivers can choose to support any one or multiple of them. Preferred
> > > recovery method will be sent in the uevent environment as WEDGED=<method>.
> > > Userspace consumers (sysadmin) can define udev rules to parse this event
> > > and take respective action to recover the device.
> > > 
> > >  Method    | Consumer expectations
> > > -----------|-----------------------------------
> > >  rebind    | unbind + rebind driver
> > >  bus-reset | unbind + reset bus device + rebind
> > >  reboot    | reboot system
> > > 
> > > v4: s/drm_dev_wedged/drm_dev_wedged_event
> > >     Use drm_info() (Jani)
> > >     Kernel doc adjustment (Aravind)
> > > v5: Send recovery method with uevent (Lina)
> > > v6: Access wedge_recovery_opts[] using helper function (Jani)
> > >     Use snprintf() (Jani)
> > > 
> > > Signed-off-by: Raag Jadav <raag.jadav at intel.com>
> > 
> > Finally caught up on mail, so dropping this here again: Please also add a
> > small section to drm-uapi.rst, pointing at these functions. Just the
> > kerneldoc for developers is kinda not enough I think.
> 
> Would you prefer a new section or have the existing one (Device reset which
> looks somewhat similar but not entirely) modified?

Great point, I think just adding a paragraph and maybe the table/list you
have to the device reset section is perfect.
-Sima
-- 
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch