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SubjectRe: [PATCH 01/15] iio: buffer-dma: Get rid of incoming/outgoing queues


Le dim., nov. 21 2021 at 19:49:03 +0100, Lars-Peter Clausen
<lars@metafoo.de> a écrit :
> 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.
>

That's still the case after the DMABUF changes of the series. Or can
you point me exactly what you think is broken?

-Paul


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