[PATCH v4 1/3] drm: Introduce device wedged event

[Asahi Lina]

On 9/6/24 6:42 PM, 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 in unrecoverable state
> and requires userspace intervention for recovery.
> 
> Purpose of this implementation is to be vendor agnostic. Userspace
> consumers (sysadmin) can define udev rules to parse this event and
> take respective action to recover the device.
> 
> Consumer expectations:
> ----------------------
> 1) Unbind driver
> 2) Reset bus device
> 3) Re-bind driver

Is this supposed to be normative? For drm/asahi we have a "wedged"
concept (firmware crashed), but the only possible recovery action is a
full system reboot (which might still be desirable to allow userspace to
trigger automatically in some scenarios) since there is no bus-level
reset and no firmware reload possible.

> 
> v4: s/drm_dev_wedged/drm_dev_wedged_event
>     Use drm_info() (Jani)
>     Kernel doc adjustment (Aravind)
> 
> Signed-off-by: Raag Jadav <raag.jadav at intel.com>
> ---
>  drivers/gpu/drm/drm_drv.c | 20 ++++++++++++++++++++
>  include/drm/drm_drv.h     |  1 +
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 93543071a500..cca5d8295eb7 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -499,6 +499,26 @@ void drm_dev_unplug(struct drm_device *dev)
>  }
>  EXPORT_SYMBOL(drm_dev_unplug);
>  
> +/**
> + * drm_dev_wedged_event - generate a device wedged uevent
> + * @dev: DRM device
> + *
> + * This generates a device wedged uevent for the DRM device specified by @dev,
> + * on the basis of which, userspace may take respective action to recover the
> + * device. Currently we only set WEDGED=1 in the uevent environment, but this
> + * can be expanded in the future.
> + */
> +void drm_dev_wedged_event(struct drm_device *dev)
> +{
> +	char *event_string = "WEDGED=1";
> +	char *envp[] = { event_string, NULL };
> +
> +	drm_info(dev, "device wedged, generating uevent\n");
> +
> +	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
> +}
> +EXPORT_SYMBOL(drm_dev_wedged_event);
> +
>  /*
>   * DRM internal mount
>   * We want to be able to allocate our own "struct address_space" to control
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index cd37936c3926..eed5e54c74fd 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -489,6 +489,7 @@ void drm_put_dev(struct drm_device *dev);
>  bool drm_dev_enter(struct drm_device *dev, int *idx);
>  void drm_dev_exit(int idx);
>  void drm_dev_unplug(struct drm_device *dev);
> +void drm_dev_wedged_event(struct drm_device *dev);
>  
>  /**
>   * drm_dev_is_unplugged - is a DRM device unplugged

~~ Lina