[PATCH v5 8/9] drm: Add aspect ratio parsing in DRM layer

[Ville Syrjälä]

On Thu, Feb 15, 2018 at 05:51:01PM +0530, Nautiyal, Ankit K wrote:
> From: "Sharma, Shashank" <shashank.sharma at intel.com>
> 
> Current DRM layer functions don't parse aspect ratio information
> while converting a user mode->kernel mode or vice versa. This
> causes modeset to pick mode with wrong aspect ratio, eventually
> causing failures in HDMI compliance test cases, due to wrong VIC.
> 
> This patch adds aspect ratio information in DRM's mode conversion
> and mode comparision functions, to make sure kernel picks mode
> with right aspect ratio (as per the VIC).
> 
> Background:
> This patch was once reviewed and merged, and later reverted due to
> lack of DRM cap protection. This is a re-spin of this patch, this
> time with DRM cap protection, to avoid aspect ratio information, when
> the client doesn't request for it.
> 
> Review link: https://pw-emeril.freedesktop.org/patch/104068/
> Background discussion: https://patchwork.kernel.org/patch/9379057/
> 
> Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
> Signed-off-by: Lin, Jia <lin.a.jia at intel.com>
> Signed-off-by: Akashdeep Sharma <akashdeep.sharma at intel.com>
> Reviewed-by: Jim Bride <jim.bride at linux.intel.com> (V2)
> Reviewed-by: Jose Abreu <Jose.Abreu at synopsys.com> (V4)
> 
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Jim Bride <jim.bride at linux.intel.com>
> Cc: Jose Abreu <Jose.Abreu at synopsys.com>
> Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> 
> V3: modified the aspect-ratio check in drm_mode_equal as per new flags
>     provided by Ville. https://patchwork.freedesktop.org/patch/188043/
> V4: rebase
> V5: rebase
> ---
>  drivers/gpu/drm/drm_modes.c | 33 ++++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index ca4c5cc..25140b9 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -1050,7 +1050,8 @@ bool drm_mode_equal(const struct drm_display_mode *mode1,
>  			      DRM_MODE_MATCH_TIMINGS |
>  			      DRM_MODE_MATCH_CLOCK |
>  			      DRM_MODE_MATCH_FLAGS |
> -			      DRM_MODE_MATCH_3D_FLAGS);
> +			      DRM_MODE_MATCH_3D_FLAGS|
> +			      DRM_MODE_MATCH_ASPECT_RATIO);

Hmm. I wonder if all the users are expecting this. Based on a cursory
examination drm_fb_helper might want to ignore the aspect ratio since
it's just looking to clone the same mode on multiple outputs. The other
cases don't look to me like they should suffer badly from this.

>  }
>  EXPORT_SYMBOL(drm_mode_equal);
>  
> @@ -1649,6 +1650,21 @@ void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
>  	out->vrefresh = in->vrefresh;
>  	out->flags = in->flags;
>  	out->type = in->type;
> +	out->flags &= ~DRM_MODE_FLAG_PIC_AR_MASK;

This looks redundant. The internal mode should not have the aspect ratio
flags set. Or are we changing that?

> +
> +	switch (in->picture_aspect_ratio) {
> +	case HDMI_PICTURE_ASPECT_4_3:
> +		out->flags |= DRM_MODE_FLAG_PIC_AR_4_3;
> +		break;
> +	case HDMI_PICTURE_ASPECT_16_9:
> +		out->flags |= DRM_MODE_FLAG_PIC_AR_16_9;
> +		break;
> +	case HDMI_PICTURE_ASPECT_RESERVED:
> +	default:
> +		out->flags |= DRM_MODE_FLAG_PIC_AR_NONE;
> +		break;
> +	}
> +
>  	strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
>  	out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
>  }
> @@ -1693,6 +1709,21 @@ int drm_mode_convert_umode(struct drm_device *dev,
>  	strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
>  	out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
>  
> +	/* Clearing picture aspect ratio bits from out flags */

What the code is doing is obvious so this comment is redundant.
The non-obvious part (ie. the "why?") is what the comment
should contain.

> +	out->flags &= ~DRM_MODE_FLAG_PIC_AR_MASK;
> +
> +	switch (in->flags & DRM_MODE_FLAG_PIC_AR_MASK) {
> +	case DRM_MODE_FLAG_PIC_AR_4_3:
> +		out->picture_aspect_ratio |= HDMI_PICTURE_ASPECT_4_3;
> +		break;
> +	case DRM_MODE_FLAG_PIC_AR_16_9:
> +		out->picture_aspect_ratio |= HDMI_PICTURE_ASPECT_16_9;
> +		break;
> +	default:
> +		out->picture_aspect_ratio = HDMI_PICTURE_ASPECT_NONE;
> +		break;
> +	}
> +
>  	out->status = drm_mode_validate_driver(dev, out);
>  	if (out->status != MODE_OK)
>  		goto out;
> -- 
> 2.7.4

-- 
Ville Syrjälä
Intel OTC