[Intel-gfx] [PATCH 10/12] drm: Don't allow multiple buffers fb with stereo modes

Daniel Vetter daniel at ffwll.ch
Tue Sep 17 06:33:22 PDT 2013

On Tue, Sep 17, 2013 at 3:20 PM, Damien Lespiau
<damien.lespiau at intel.com> wrote:
> On Tue, Sep 17, 2013 at 12:37:48PM +0200, Daniel Vetter wrote:
>> I guess we should start to check that. For 3d framebuffers with 2
>> separate buffer handles for each plane I think we need to add another flag
>> to addfb2, e.g.
>> #define DRM_MODE_FB_3D_2_FRAMES (1<<1) /* separate left/right buffers, doubles plane count */
>> and then also throw in the respective check code into the core that
>> userspace supplies sufficient amounts of buffers in framebuffer_check()
>> by adjusting drM_format_num_planes and drm_format_plane_cpp.
> Would we really need that flag? we can just count the number of buffers
> and decide from that number whether we're in the 1 or 2 buffer(s) case?

We do not know at addfb2 time that it'll be a 3d mode buffer, and
drivers might want to know that to internally assign the buffers to
left/right buffer handle pointers. Similar to how we already have a
flag for when the buffer is interlaced, which atm we don't support
(since we only support scan-out of progressive buffers to interlaced
modes, not interlaced to interlaced). So imo a flag here makes sense
so that the driver can properly check constraints and make sense of
the handles.
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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