How to handle DRM crtc_id, connector_id greater than 31

[Pekka Paalanen]

On Tue, 6 Dec 2016 16:21:30 -0800
Miguel Angel Vico <mvicomoya at nvidia.com> wrote:

> Hi Eric,
> 
> The problem here is we are using crtc_id and connector_id as indexes,
> while they aren't.
> 
> Nothing keeps DRM drivers from advertising CRTC and connectors with ids
> that aren't sequential and starting at 0 or 1.

Hi,

yes, we at Collabora have recently discovered this problem too.

> The right fix is to use indexes instead of ids to update bitmasks.
> 
> drm_output::pipe stores the CRTC index and can be used to update CRTC
> bitmasks.

Somehow I don't think that's a good plan.

> For connectors, we need to add something similar.

No, there are simpler solutions. We should keep track of the ids. The
currently-in-use ids are already discoverable through the list of
weston_outputs. We just needs arrays of ids for the other uses.

The bit masks should just go.


Thanks,
pq

> On Mon, 5 Dec 2016 21:49:40 +0000
> "Ruei, Eric" <e-ruei1 at ti.com> wrote:
> 
> > To whom it may concern:
> > 
> > We have encountered a Weston hotplug issue with DRM backend where the
> > hotplug of HDMI connector caused unexpected Weston exit recently. The
> > root cause of the problem is that the DRM connector id of the HDMI
> > display exceeds 31, but the corresponding active bitmap variable
> > connector_allocator is only 32-bit. The same issue is also applicable
> > to the DRM instance variable crtc_allocator and all the local
> > variables of CRTC or connector bitmap.  A tentative quick fix is to
> > increase the size of bitmap variable from uint32_t to uint64_t, but
> > it will break again when the DRM id exceeds 63. 
> > 
> > Attached please find our tentative patch against Weston 1.9 as your
> > reference.
> > 
> > Best regards,
> > 
> > Eric
> > 
> >   
> 
> 

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