Messages in this thread | | | Subject | Re: [PATCH] [media] vb2: map dmabuf for planes on driver queue instead of vidioc_qbuf | From | Javier Martinez Canillas <> | Date | Mon, 18 Jul 2016 10:15:14 -0400 |
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Hello Hans, Michael and Marek,
Thanks a lot for your feedback.
On 07/18/2016 04:34 AM, Hans Verkuil wrote: > On 07/15/2016 06:26 PM, Javier Martinez Canillas wrote: >> The buffer planes' dma-buf are currently mapped when buffers are queued >> from userspace but it's more appropriate to do the mapping when buffers >> are queued in the driver since that's when the actual DMA operation are >> going to happen. > > Does this solve anything? Once the DMA has started the behavior is the same > as before (QBUF maps the dmabuf), only while the DMA engine hasn't started > yet are the QBUF calls just accepted and the mapping takes place when the > DMA is kickstarted. This makes QBUF behave inconsistently. > > You don't describe here WHY this change is needed. >
Nicolas pointed me to the TODO and suggested me the patch for the reasons he explained in his latest email. And yes, this should had been tagged as a RFC and just to know what you think about it. Sorry for missing that.
> I'm not sure I agree with the TODO, and even if I did, I'm not sure I agree > with this solution. Since queuing the buffer to the driver is not the same > as 'just before the DMA', since there may be many buffers queued up in the > driver and you don't know in vb2 when the buffer is at the 'just before the DMA' > stage. >
Right, I meant "as closer as possible to when the actual DMA is going to happen" rather than "just before the DMA".
> Regards, > > Hans >
Best regards, -- Javier Martinez Canillas Open Source Group Samsung Research America
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