[Mesa-dev] [PATCH 5/5] [v2] gbm: Export a per plane getter for offset

[Jason Ekstrand]

On Thu, Mar 23, 2017 at 6:16 AM, Daniel Stone <daniel at fooishbar.org> wrote:

> Hi,
>
> On 8 March 2017 at 05:31, Ben Widawsky <ben at bwidawsk.net> wrote:
> > Unlike stride, there was no previous offset getter, so it can be right
> > on the first try.
> >
> > v2: Return EINVAL when plane is greater than total planes to make it
> > match the similar APIs.
> > Avoid leak after fromPlanar (Daniel)
> > Make sure when getting offsets we consider dumb images (Daniel)
> >
> > v3: Use Jason's recommendation for handling the non-planar case.
> >
> > v4: Return int64_t so we can get real errors
>
> I really wish I'd caught this earlier. :(
>
> Returning int64_t is annoying because the relevant interface demands
> we need uint32_t, so we need to do casts in users. Given that the
> offset is useless without the handle/fd, and we have real error values
> for those (0 for handle, -1 for fd) which don't require casts, I'd
> much rather this was just a uint32_t returning 0 on failure.
>
> Oh well. If it's too late to change then fine, but if we could change
> it, it would make life a little easier.
>

I'm ok with changing it given that we know there are zero users and it's
been in-tree for all of a week.

The only problem is that 0 is a perfectly valid offset.  I think we could
use (uint32_t)-1 and that would probably be safe.
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