Re: [RFC PATCH 3/5] drm/i915: Expose logical engine instance to user

From: Daniel Vetter <daniel@ffwll.ch>
To: Matthew Brost <matthew.brost@intel.com>
Cc: tony.ye@intel.com, tvrtko.ursulin@intel.com,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	carl.zhang@intel.com, jason.ekstrand@intel.com,
	daniele.ceraolospurio@intel.com, jon.bloomfield@intel.com,
	daniel.vetter@intel.com, john.c.harrison@intel.com
Subject: Re: [RFC PATCH 3/5] drm/i915: Expose logical engine instance to user
Date: Tue, 11 May 2021 16:53:34 +0200	[thread overview]
Message-ID: <YJqabmnUEjwi8iAJ@phenom.ffwll.local> (raw)
In-Reply-To: <20210506173049.72503-4-matthew.brost@intel.com>

On Thu, May 06, 2021 at 10:30:47AM -0700, Matthew Brost wrote:
> Expose logical engine instance to user via query engine info IOCTL. This
> is required for split-frame workloads as these need to be placed on
> engines in a logically contiguous order. The logical mapping can change
> based on fusing. Rather than having user have knowledge of the fusing we
> simply just expose the logical mapping with the existing query engine
> info IOCTL.
> 
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Tony Ye <tony.ye@intel.com>
> CC: Carl Zhang <carl.zhang@intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Jason Ekstrand <jason@jlekstrand.net>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  include/uapi/drm/i915_drm.h | 7 ++++++-

Two things on all these 3 patches:

- Until we've merged the uapi it shouldn't show up in uapi headers. See
  what Matt A. has done with a fake local header in Documentation/gpu/rfc
  which you can pull in.

- Since this one is tiny I think just the text in the rfc is good enough,
  I'd drop this.

- Squash the others in with the parallel submit rfc patch so that the
  structs and long-form text are all in one patch please, makes reviewing
  the overall thing a bit simpler. Rule is to have a complete change per
  patch, and then not split things further.

>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 9f331ad629f5..26d2e135aa31 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -2396,14 +2396,19 @@ struct drm_i915_engine_info {
>  
>  	/** @flags: Engine flags. */
>  	__u64 flags;
> +#define I915_ENGINE_INFO_HAS_LOGICAL_INSTANCE		(1 << 0)
>  
>  	/** @capabilities: Capabilities of this engine. */
>  	__u64 capabilities;
>  #define I915_VIDEO_CLASS_CAPABILITY_HEVC		(1 << 0)
>  #define I915_VIDEO_AND_ENHANCE_CLASS_CAPABILITY_SFC	(1 << 1)
>  
> +	/** Logical engine instance */

I think in the final version that we merge with the uapi this should:
- explain why we need this
- link to relevant other uapi like the paralle submit extension

Cheers, Daniel

> +	__u16 logical_instance;
> +
>  	/** @rsvd1: Reserved fields. */
> -	__u64 rsvd1[4];
> +	__u16 rsvd1[3];
> +	__u64 rsvd2[3];
>  };
>  
>  /**
> -- 
> 2.28.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch