x11: allow disabling DRI3 via LIBVA_DRI3_DISABLE env var

[evelikov]

There are some corner cases where DRI3 does not work correctly. While bug reports are appreciated, this enables users to get back to their machines in meaningful way - aka w/o having to rebuild libva.

---

@dvrogozh@XinfengZhang can we roll a 2.17.1 release with this fix? There is a PR incoming, which will be quiet large and evasive for a bugfix release.

Thanks o/

[XinfengZhang]

yes, of course, if we merge it, we could cherry pick it to 2.17 branch , to have a hotfix release. but I am wondering whether it is a real fix. customer still need to manually set the env ...

[evelikov]

This not a fix but a workaround that we want now. Mesa had an equivalent for years.

It serves people who want to (or need to) disable the DRI3 code path for testing or debugging purposes. Imagine a really weird bug gets reported tomorrow and fixing that requires months until it's actually hits a libva release. In the interim people can use the override to have working systems.

[dvrogozh]

looks good

[zhmars]

Hi, could we consider adding similar changes to va_DisplayContextGetNumCandidates()? Without this, hardware video decoding on chromium still broken in my test.

diff --git a/va/x11/va_x11.c b/va/x11/va_x11.c
index a612c20..81cc972 100644
--- a/va/x11/va_x11.c+++ b/va/x11/va_x11.c@@ -195,9 +195,10 @@ static VAStatus va_DisplayContextGetNumCandidates(
int *num_candidates
)
{
- VAStatus vaStatus;+ VAStatus vaStatus = VA_STATUS_ERROR_UNKNOWN;- vaStatus = va_DRI3_GetNumCandidates(pDisplayContext, num_candidates);+ if (!getenv("LIBVA_DRI3_DISABLE"))+ vaStatus = va_DRI3_GetNumCandidates(pDisplayContext, num_candidates);
if (vaStatus != VA_STATUS_SUCCESS)
vaStatus = va_DRI2_GetNumCandidates(pDisplayContext, num_candidates);

[evelikov]

Indeed good point - opened #689 with details. Thanks o/