Messages in this thread | | | Date | Wed, 10 Dec 2008 12:58:09 -0700 | From | "Dan Williams" <> | Subject | Re: [PATCH 1/4 v2] dmaengine: add a tx_free method to struct dma_async_tx_descriptor |
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On Wed, Dec 10, 2008 at 3:36 AM, Guennadi Liakhovetski <g.liakhovetski@gmx.de> wrote: > From: Guennadi Liakhovetski <lg@denx.de> > > Some users reuse DMA transaction descriptors multiple times and need an > explicit call to release them. An example of such a user is Video4Linux, which > has to be able to release descriptors on ioctl(VIDIOC_DQBUF). > > Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Hi Guennadi,
Other dmaengine drivers have tasklets that scan the list of completed descriptors and free the "acked" ones. This happens in the cleanup tasklet... /me looks ...hmm this driver does not have a cleanup routine? Ideally support for ioctl(VIDIOC_DQBUF) could be achieved through this mechanism without needing to increase the size of dma_async_tx_descriptor (which has cache utilization impacts on other drivers).
-- Dan
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