Re: [PATCH v2] drm/i915: Introduce struct class_instance for engines across the uAPI

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 12/04/2019 08:14, Chris Wilson wrote:
> SSEU reprogramming of the context introduced the notion of engine class
> and instance for a forwards compatible method of describing any engine
> beyond the old execbuf interface. We wish to adopt this class:instance
> description for more interfaces, so pull it out into a separate type for
> userspace convenience.
> 
> References: e46c2e99f600 ("drm/i915: Expose RPCS (SSEU) configuration to userspace (Gen11 only)")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
> Cc: Tony Ye <tony.ye@intel.com>
> Cc: Andi Shyti <andi@etezian.org>
> ---
> Drop the union foible. It's only going to hinder a decision ;)
> -Chris
> ---
>   drivers/gpu/drm/i915/i915_gem_context.c |  8 ++++----
>   include/uapi/drm/i915_drm.h             | 16 ++++++++++++++--
>   2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 7fc34ab6df87..dd728b26b5aa 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -1386,8 +1386,8 @@ static int set_sseu(struct i915_gem_context *ctx,
>   		return -EINVAL;
>   
>   	engine = intel_engine_lookup_user(i915,
> -					  user_sseu.engine_class,
> -					  user_sseu.engine_instance);
> +					  user_sseu.engine.engine_class,
> +					  user_sseu.engine.engine_instance);
>   	if (!engine)
>   		return -EINVAL;
>   
> @@ -1626,8 +1626,8 @@ static int get_sseu(struct i915_gem_context *ctx,
>   		return -EINVAL;
>   
>   	engine = intel_engine_lookup_user(ctx->i915,
> -					  user_sseu.engine_class,
> -					  user_sseu.engine_instance);
> +					  user_sseu.engine.engine_class,
> +					  user_sseu.engine.engine_instance);
>   	if (!engine)
>   		return -EINVAL;
>   
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 52051d24d89d..bbc453b1e50f 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -126,6 +126,19 @@ enum drm_i915_gem_engine_class {
>   	I915_ENGINE_CLASS_INVALID	= -1
>   };
>   
> +
> +/*
> + * There may be more than one engine fulfilling any role within the system.
> + * Each engine of a class is given a unique instance number and therefore
> + * any engine can be specified by its class:instance tuplet. APIs that allow
> + * access to any engine in the system will use struct i915_engine_class_instance
> + * for this identification.
> + */
> +struct i915_engine_class_instance {
> +	__u16 engine_class; /* see enum drm_i915_gem_engine_class */
> +	__u16 engine_instance;
> +};
> +
>   /**
>    * DOC: perf_events exposed by i915 through /sys/bus/event_sources/drivers/i915
>    *
> @@ -1525,8 +1538,7 @@ struct drm_i915_gem_context_param_sseu {
>   	/*
>   	 * Engine class & instance to be configured or queried.
>   	 */
> -	__u16 engine_class;
> -	__u16 engine_instance;
> +	struct i915_engine_class_instance engine;
>   
>   	/*
>   	 * Unused for now. Must be cleared to zero.
> 

This will definitely be tidier in the near future (despite a bit of 
ugliness in engine.engine_*). I have also checked that this indeed is 
part of 5.1 which hasn't been shipped yet.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

If we can get an ack from Joonas and Tony, to whom it probably falls to 
do the media-driver change I think we are good to do.

Regards,

Tvrtko
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