[PATCH 4/4] drm: Renesas SH Mobile DRM driver

[Lars-Peter Clausen]

On 05/30/2012 04:45 PM, Lars-Peter Clausen wrote:
> On 05/30/2012 02:32 PM, Laurent Pinchart wrote:
>> [...]
>> +	for (i = 0; i < (format->yuv ? 2 : 1); ++i) {
>> +		obj = drm_gem_object_lookup(dev, file_priv,
>> +					    mode_cmd->handles[i]);
>> +		if (obj == NULL) {
>> +			dev_dbg(dev->dev, "GEM object %u not found\n",
>> +				mode_cmd->handles[i]);
>> +			ret = -ENOENT;
>> +			goto error;
>> +		}
>> +		sfb->sobj[i] = to_shmob_gem_object(obj);
>> +	}
>> +
> 
> I added multi-plane support the cma fb helper functions and it seems to
> work. But all other DRM drivers seem to assume that multi-plane formats
> still only have a single buffer, while yours seems to assume that there is a
> plane for each buffer. The exception is the Exynos driver, but it added a
> new set of formats which are identical to the other formats, but use one
> buffer per plane.
> 
> So I'm not sure how to implement this correctly in a generic fashion.
> 

This post by Ville Syrjälä seems to explain it quite well:
http://lists.freedesktop.org/archives/dri-devel/2012-April/021044.html