Does gbm_bo_map() implicitly synchronise?

[Christian König]

Am 17.06.24 um 16:50 schrieb Michel Dänzer:
> On 2024-06-17 12:29, Pierre Ossman wrote:
>> Just to avoid any uncertainty, are both of these things done implicitly by gbm_bo_map()/gbm_bo_unmap()?
>>
>> I did test adding those steps just in case, but unfortunately did not see an improvement. My order was:
>>
>> 1. gbm_bo_import(GBM_BO_USE_RENDERING)
>> 2. gbm_bo_get_fd()
>> 3. Wait for client to request displaying the buffer
>> 4. gbm_bo_map(GBM_BO_TRANSFER_READ)
>> 5. select(fd+1, &fds, NULL, NULL, NULL)
> *If* select() is needed, it needs to be before gbm_bo_map(), because the latter may perform a blit from the real BO to a staging one for CPU access.

But don't you then need to wait for the blit to finish?

Regards,
Christian.

>
>
>> 6. ioctl(DMA_BUF_IOCTL_SYNC, &{ .flags = DMA_BUF_SYNC_START | DMA_BUF_SYNC_READ })
> gbm_bo_map() should do this internally if needed.
>
>
>> 7. pixman_blt()
>> 8. gbm_bo_unmap()
>