Messages in this thread | | | Subject | Re: [PATCH 01/15] iio: buffer-dma: Get rid of incoming/outgoing queues | From | Lars-Peter Clausen <> | Date | Sun, 21 Nov 2021 19:49:03 +0100 |
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On 11/21/21 6:52 PM, Paul Cercueil wrote: > Hi Lars, > > Le dim., nov. 21 2021 at 17:23:35 +0100, Lars-Peter Clausen > <lars@metafoo.de> a écrit : >> On 11/15/21 3:19 PM, Paul Cercueil wrote: >>> The buffer-dma code was using two queues, incoming and outgoing, to >>> manage the state of the blocks in use. >>> >>> While this totally works, it adds some complexity to the code, >>> especially since the code only manages 2 blocks. It is much easier to >>> just check each block's state manually, and keep a counter for the next >>> block to dequeue. >>> >>> Since the new DMABUF based API wouldn't use these incoming and outgoing >>> queues anyway, getting rid of them now makes the upcoming changes >>> simpler. >>> >>> Signed-off-by: Paul Cercueil <paul@crapouillou.net> >> The outgoing queue is going to be replaced by fences, but I think we >> need to keep the incoming queue. > > Blocks are always accessed in sequential order, so we now have a > "queue->next_dequeue" that cycles between the buffers allocated for > fileio. > >>> [...] >>> @@ -442,28 +435,33 @@ EXPORT_SYMBOL_GPL(iio_dma_buffer_disable); >>> static void iio_dma_buffer_enqueue(struct iio_dma_buffer_queue >>> *queue, >>> struct iio_dma_buffer_block *block) >>> { >>> - if (block->state == IIO_BLOCK_STATE_DEAD) { >>> + if (block->state == IIO_BLOCK_STATE_DEAD) >>> iio_buffer_block_put(block); >>> - } else if (queue->active) { >>> + else if (queue->active) >>> iio_dma_buffer_submit_block(queue, block); >>> - } else { >>> + else >>> block->state = IIO_BLOCK_STATE_QUEUED; >>> - list_add_tail(&block->head, &queue->incoming); >> If iio_dma_buffer_enqueue() is called with a dmabuf and the buffer is >> not active, it will be marked as queued, but we don't actually keep a >> reference to it anywhere. It will never be submitted to the DMA, and >> it will never be signaled as completed. > > We do keep a reference to the buffers, in the queue->fileio.blocks > array. When the buffer is enabled, all the blocks in that array that > are in the "queued" state will be submitted to the DMA. > But not when used in combination with the DMA buf changes later in this series.
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