Does gbm_bo_map() implicitly synchronise?

[Christian König]

Am 17.06.24 um 16:55 schrieb Michel Dänzer:
> On 2024-06-17 16:52, Christian König wrote:
>> 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?
> No, gbm_bo_map() must handle that internally. When it returns, the CPU must see the correct contents.

Ah, ok in that case that function does more than I expected.

Thanks,
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()