[PATCHv4 04/13] drm/shmobile: Restrict plane loops to only operate on legacy planes

[Daniel Vetter]

On Fri, Mar 28, 2014 at 04:50:13PM +0100, Laurent Pinchart wrote:
> Hi Matt,
> 
> Thank you for the patch.
> 
> On Thursday 27 March 2014 17:44:29 Matt Roper wrote:
> > Ensure that existing driver loops over all planes do not change behavior
> > when we begin adding new types of planes (primary and cursor) to the DRM
> > plane list in future patches.
> > 
> > Cc: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> > Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> 
> Acked-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> I have a question though. The patch set introduces three plane types, OVERLAY, 
> PRIMARY and CURSOR. What should a driver that has no concept of primary plane 
> do ? Expose all planes as OVERLAY planes only ?

It's a matter of backwards compat with old userspace. primary/cursor are
simply ways to tell the drm core which planes to use to forward the legacy
cursor crtc and which plane will be used for the framebuffer in setCrtc.

So until we have the new atomic interface ready your driver kinda needs to
expose at least a primary plane, otherwise there's no way to even switch
on the crtc.

But besides this backwards compat issue there's no difference and you can
specify whatever plane you want as primary/cursor (or none if you don't
care about old userspace).
-Daniel

> 
> > ---
> >  drivers/gpu/drm/shmobile/shmob_drm_crtc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/shmobile/shmob_drm_crtc.c
> > b/drivers/gpu/drm/shmobile/shmob_drm_crtc.c index 0428076..ea543b4 100644
> > --- a/drivers/gpu/drm/shmobile/shmob_drm_crtc.c
> > +++ b/drivers/gpu/drm/shmobile/shmob_drm_crtc.c
> > @@ -247,7 +247,7 @@ static void shmob_drm_crtc_start(struct shmob_drm_crtc
> > *scrtc) lcdc_write(sdev, LDDDSR, value);
> > 
> >  	/* Setup planes. */
> > -	list_for_each_entry(plane, &dev->mode_config.plane_list, head) {
> > +	drm_for_each_legacy_plane(plane, &dev->mode_config.plane_list) {
> >  		if (plane->crtc == crtc)
> >  			shmob_drm_plane_setup(plane);
> >  	}
> 
> -- 
> Regards,
> 
> Laurent Pinchart
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch