The problem occurs in the following situation:
1. Create Pixmap
2. Software fallback on pixmap: pExaPixmap->pDamage created
3. Accel to pixmap: driver pixmap created, exaPixmapIsOffscreen() now true
4. Software fallback on pixmap
4.1: PrepareAccess() from driver succeeds, so no DFS to system memory copy
4.2: Software rendering...
4.3: (pExaPixmap->pDamage && exaPixmapIsOffscreen()) is true, so we try
to (incorrectly) UTS the data back to the driver pixmap, when we
should just call the driver's FinishAccess() hook.
4.4: fail
The patch adds an additional check on pExaPixmap->offscreen, which should
(for the cases exaPixmapIsOffscreen() will return true) only be FALSE
when we haven't used PrepareAccess() on the pixmap.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Acked-By: Michel Dänzer <michel@daenzer.net>
[ Michel Dänzer: This is a 'backport' of commit
647b79f87a from master - actually this patch
was submitted first but didn't apply to master anymore, so technically the
other change is a 'forward port' of this one ]
If the PrepareAccess hook fails, use the DownloadFromScreen hook to retrieve
driver pixmap contents to a system RAM copy, perform software rendering on that
and copy the results back using the UploadToScreen hook. Use the classic
migration logic to minimize transfers (which as a bonus allows slightly
cleaning up some of the existing mixed pixmap code).
This enables things that weren't possible before with driver-allocated pixmap
storage: If some (or all) GPU pixmap storage can't be mapped directly by the
CPU, this can be handled between the PrepareAccess and
DownloadFrom/UploadToScreen hooks, e.g.:
* Radeon KMS on big endian machines can fail PrepareAccess if the pixmap
requires byte-swapping and swap bytes in DownloadFrom/UploadToScreen.
* Environments where GPU and CPU don't have a shared address space at all.
Here the driver PrepareAccess hook will always fail and leave all transfers
between GPU / CPU storage to the Download/From/UploadToScreen hooks.
Drivers which can handle all pixmaps in the PrepareAccess hook should notice
little if any difference.
(cherry picked from commit 1818cbd70f)
- Based on driver pixmaps with some changes (completely transparent to driver).
- It helps with the problem of known software fallbacks, such as trapezoids.
- exaDoMigration is now called for all cases that provide a do_migration hook.
- exa_migration.c is renamed to exa_migration_classic.c
