From: Daniel Vetter <firstname.lastname@example.org>
To: Pekka Paalanen <email@example.com>
Cc: firstname.lastname@example.org, email@example.com,
Leandro Ribeiro <firstname.lastname@example.org>
Subject: Re: [PATCH v2 1/1] drm/doc: document drm_mode_get_plane
Date: Tue, 27 Apr 2021 11:00:24 +0200 [thread overview]
Message-ID: <YIfSqPq6J4sI6PyI@phenom.ffwll.local> (raw)
On Tue, Apr 27, 2021 at 10:40:24AM +0300, Pekka Paalanen wrote:
> On Mon, 26 Apr 2021 14:30:53 -0300
> Leandro Ribeiro <email@example.com> wrote:
> > On 4/26/21 7:58 AM, Simon Ser wrote:
> > > On Monday, April 26th, 2021 at 9:36 AM, Pekka Paalanen <firstname.lastname@example.org> wrote:
> > >
> > >>>> This should probably explain what the bits in the mask correspond to.
> > >>>> As in, which CRTC does bit 0 refer to, and so on.
> > >>>
> > >>> What about:
> > >>>
> > >>> "possible_crtcs: Bitmask of CRTC's compatible with the plane. CRTC's are
> > >>> created and they receive an index, which corresponds to their position
> > >>> in the bitmask. CRTC with index 0 will be in bit 0, and so on."
> > >>
> > >> This would still need to explain where can I find this index.
> > >
> > What do you mean?
> > > This closed merge request had some docs about possible CRTCs:
> > >
> > > https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/102
> > >
> > I'm afraid I don't know exactly what you expect to be documented here
> > that is still missing. Could you please elaborate?
> > Thanks a lot!
> The documentation you add is talking about "CRTC index". What defines a
> CRTC object's index? How do I determine what index a CRTC object has?
> The answer is, AFAIK, that the index is never stored explicitly
> anywhere. You have to get the DRM resources structure, which has an
> array for CRTC IDs. The index is the index to that array, IIRC. So if
> one does not already know this, it is going to be really hard to figure
> out what the "index" is. It might even be confused with the object ID,
> which it is not but the ID might by complete accident be less than 32
> so it would look ok at first glance.
> If the index is already explained somewhere else, a reference to that
> documentation would be enough.
I think if we do this we should have a DOC: section in the drm_mode.h uapi
header which explains how the index is computed, and then we reference
that everywhere. Because otherwise there's going to be a _lot_ of
duplication of this all over. Kernel-internally we solve this by just
referencing drm_foo_index() family of functions, but for the uapi there's
really nothing, so needs text.
Software Engineer, Intel Corporation
dri-devel mailing list
next prev parent reply other threads:[~2021-04-27 9:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 18:10 [PATCH v2 0/1] Document drm_mode_get_plane Leandro Ribeiro
2021-04-22 18:10 ` [PATCH v2 1/1] drm/doc: document drm_mode_get_plane Leandro Ribeiro
2021-04-23 11:11 ` Pekka Paalanen
2021-04-23 21:30 ` Leandro Ribeiro
2021-04-26 7:36 ` Pekka Paalanen
2021-04-26 10:58 ` Simon Ser
2021-04-26 17:30 ` Leandro Ribeiro
2021-04-27 7:40 ` Pekka Paalanen
2021-04-27 9:00 ` Daniel Vetter [this message]
2021-04-28 21:42 ` Leandro Ribeiro
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