[Intel-gfx] [PATCH] drm/i915/gt: Add a comment about how to use udev for configuring engines

[Joonas Lahtinen]

Quoting Chris Wilson (2020-12-21 15:01:05)
> We expose engine properties under sysfs so that the sysadmin can
> configure the driver according to their requirements. We can also use
> udev rules to then apply that configuration anytime a device is
> reloaded. Include a udev snippet provided by Joonas as an example.
> 
> v2: Update the snippet
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gt/sysfs_engines.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/sysfs_engines.c b/drivers/gpu/drm/i915/gt/sysfs_engines.c
> index 9cf943b6a44b..37f078e69a42 100644
> --- a/drivers/gpu/drm/i915/gt/sysfs_engines.c
> +++ b/drivers/gpu/drm/i915/gt/sysfs_engines.c
> @@ -11,6 +11,22 @@
>  #include "intel_engine_heartbeat.h"
>  #include "sysfs_engines.h"
>  
> +/*
> + * The sysfs provides a means for configuring each engine for the intended
> + * usecase, and by utilising a udev the configuration can be made persistent
> + * across reboots and device rebinding.
> + *
> + * An example udev rule to run a custom sysadmin script would be,
> + * /etc/udev/rules.d/50-intel-gpu.rules:
> + *
> + * ACTION=="bind|add",SUBSYSTEM=="pci",DRIVER=="i915",RUN+="/usr/local/libexec/i915-disable-preempt-timeout.sh"
> + *
> + * where the script receives the device name and can open the sysfs, e.g.:
> + * for ENGINE in $(find /sys/$DEVPATH/drm/card?/engine -maxdepth 1) do
> + *   echo 0 > $ENGINE/preempt_timeout_ms # Disable reset on preemption failure
> + * done
> + */

If we just could get this into the output of 'make htmldocs', it would
be good.

Regards, Joonas

> +
>  struct kobj_engine {
>         struct kobject base;
>         struct intel_engine_cs *engine;
> -- 
> 2.20.1
>