Messages in this thread | | | Date | Wed, 8 Nov 2023 14:22:23 +0100 | Subject | Re: [PATCH v14 08/56] media: videobuf2: Use vb2_get_num_buffers() helper | From | Benjamin Gaignard <> |
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Le 08/11/2023 à 10:42, Tomasz Figa a écrit : > On Tue, Oct 31, 2023 at 05:30:16PM +0100, Benjamin Gaignard wrote: >> Stop using queue num_buffers field directly, instead use >> vb2_get_num_buffers(). >> This prepares for the future 'delete buffers' feature where there are >> holes in the buffer indices. >> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com> >> --- >> .../media/common/videobuf2/videobuf2-core.c | 92 +++++++++++-------- >> .../media/common/videobuf2/videobuf2-v4l2.c | 4 +- >> 2 files changed, 54 insertions(+), 42 deletions(-) >> >> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c >> index b406a30a9b35..c5c5ae4d213d 100644 >> --- a/drivers/media/common/videobuf2/videobuf2-core.c >> +++ b/drivers/media/common/videobuf2/videobuf2-core.c >> @@ -444,13 +444,14 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory, >> unsigned int num_buffers, unsigned int num_planes, >> const unsigned plane_sizes[VB2_MAX_PLANES]) >> { >> + unsigned int q_num_buffers = vb2_get_num_buffers(q); >> unsigned int buffer, plane; >> struct vb2_buffer *vb; >> int ret; >> >> /* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */ >> num_buffers = min_t(unsigned int, num_buffers, >> - VB2_MAX_FRAME - q->num_buffers); >> + VB2_MAX_FRAME - q_num_buffers); > I guess it's safe in this specific situation, but was there any reason > behind not just calling vb2_get_num_buffers() directly here? > >> >> for (buffer = 0; buffer < num_buffers; ++buffer) { >> /* Allocate vb2 buffer structures */ >> @@ -470,7 +471,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory, >> vb->planes[plane].min_length = plane_sizes[plane]; >> } >> >> - vb2_queue_add_buffer(q, vb, q->num_buffers + buffer); >> + vb2_queue_add_buffer(q, vb, q_num_buffers + buffer); > In this case it should also be fine, but actually now this is a loop and if > somone doesn't know what the other code in the loop does, one could be > concerned that the num buffers actually could have changed, but we still > use the cached one that we got at the beginning of the function. > > (Ideally I'd imagine vb2_queue_add_buffer() to append the buffer > at the end of the queue and increment the num_buffers internally, but it > doesn't have to happen now, as this series is already quite complex...)
That will be the case later in the series when I replace num_buffers field by a bitmap. Until that I prefer to limit the changes in this loop.
> >> call_void_bufop(q, init_buffer, vb); >> >> /* Allocate video buffer memory for the MMAP type */ > [snip] >> @@ -2513,7 +2519,8 @@ void vb2_core_queue_release(struct vb2_queue *q) >> __vb2_cleanup_fileio(q); >> __vb2_queue_cancel(q); >> mutex_lock(&q->mmap_lock); >> - __vb2_queue_free(q, q->num_buffers); >> + __vb2_queue_free(q, vb2_get_num_buffers(q)); >> + q->num_buffers = 0; > Unrelated change?
No because I found a case where q->num_buffers wasn't correctly reset while testing.
> >> mutex_unlock(&q->mmap_lock); >> } >> EXPORT_SYMBOL_GPL(vb2_core_queue_release); >> @@ -2542,7 +2549,7 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file, >> /* >> * Start file I/O emulator only if streaming API has not been used yet. >> */ >> - if (q->num_buffers == 0 && !vb2_fileio_is_active(q)) { >> + if (vb2_get_num_buffers(q) == 0 && !vb2_fileio_is_active(q)) { >> if (!q->is_output && (q->io_modes & VB2_READ) && >> (req_events & (EPOLLIN | EPOLLRDNORM))) { >> if (__vb2_init_fileio(q, 1)) >> @@ -2580,7 +2587,7 @@ __poll_t vb2_core_poll(struct vb2_queue *q, struct file *file, >> * For output streams you can call write() as long as there are fewer >> * buffers queued than there are buffers available. >> */ >> - if (q->is_output && q->fileio && q->queued_count < q->num_buffers) >> + if (q->is_output && q->fileio && q->queued_count < vb2_get_num_buffers(q)) >> return EPOLLOUT | EPOLLWRNORM; >> >> if (list_empty(&q->done_list)) { >> @@ -2629,8 +2636,8 @@ struct vb2_fileio_buf { >> * struct vb2_fileio_data - queue context used by file io emulator >> * >> * @cur_index: the index of the buffer currently being read from or >> - * written to. If equal to q->num_buffers then a new buffer >> - * must be dequeued. >> + * written to. If equal to number of already queued buffers >> + * then a new buffer must be dequeued. > Hmm, that's a significant meaning change compared to the original text. Is > it indended?
Does "If equal to number of buffers in the vb2_queue then a new buffer must be dequeued." sound better for you ?
> >> * @initial_index: in the read() case all buffers are queued up immediately >> * in __vb2_init_fileio() and __vb2_perform_fileio() just cycles >> * buffers. However, in the write() case no buffers are initially >> @@ -2640,7 +2647,7 @@ struct vb2_fileio_buf { >> * buffers. This means that initially __vb2_perform_fileio() >> * needs to know what buffer index to use when it is queuing up >> * the buffers for the first time. That initial index is stored >> - * in this field. Once it is equal to q->num_buffers all >> + * in this field. Once it is equal to num_buffers all > It's not clear what num_buffers means here. Would it make sense to instead > say "number of buffers in the vb2_queue"?
Yes I will change that
> >> * available buffers have been queued and __vb2_perform_fileio() >> * should start the normal dequeue/queue cycle. >> * >> @@ -2690,7 +2697,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read) >> /* >> * Check if streaming api has not been already activated. >> */ >> - if (q->streaming || q->num_buffers > 0) >> + if (q->streaming || vb2_get_num_buffers(q) > 0) >> return -EBUSY; >> >> /* >> @@ -2740,7 +2747,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read) >> /* >> * Get kernel address of each buffer. >> */ >> - for (i = 0; i < q->num_buffers; i++) { >> + for (i = 0; i < vb2_get_num_buffers(q); i++) { >> /* vb can never be NULL when using fileio. */ >> vb = vb2_get_buffer(q, i); >> >> @@ -2759,18 +2766,23 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read) >> /* >> * Queue all buffers. >> */ >> - for (i = 0; i < q->num_buffers; i++) { >> - ret = vb2_core_qbuf(q, q->bufs[i], NULL, NULL); >> + for (i = 0; i < vb2_get_num_buffers(q); i++) { >> + struct vb2_buffer *vb2 = vb2_get_buffer(q, i); >> + >> + if (!vb2) >> + continue; >> + >> + ret = vb2_core_qbuf(q, vb2, NULL, NULL); >> if (ret) >> goto err_reqbufs; >> fileio->bufs[i].queued = 1; >> } > Doesn't this part belong to the previous patch that changes q->bufs[x] to > vb2_get_buffer()?
Yes I will change that too.
> >> /* >> * All buffers have been queued, so mark that by setting >> - * initial_index to q->num_buffers >> + * initial_index to num_buffers > What num_buffers?
I will use your wording: "the number of buffers in the vb2_queue"
> >> */ >> - fileio->initial_index = q->num_buffers; >> - fileio->cur_index = q->num_buffers; >> + fileio->initial_index = vb2_get_num_buffers(q); >> + fileio->cur_index = fileio->initial_index; >> } >> >> /* >> @@ -2964,12 +2976,12 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_ >> * If we are queuing up buffers for the first time, then >> * increase initial_index by one. >> */ >> - if (fileio->initial_index < q->num_buffers) >> + if (fileio->initial_index < vb2_get_num_buffers(q)) >> fileio->initial_index++; >> /* >> * The next buffer to use is either a buffer that's going to be >> - * queued for the first time (initial_index < q->num_buffers) >> - * or it is equal to q->num_buffers, meaning that the next >> + * queued for the first time (initial_index < num_buffers) >> + * or it is equal to num_buffers, meaning that the next > What num_buffers?
Same here
> > Best regards, > Tomasz > _______________________________________________ > Kernel mailing list -- kernel@mailman.collabora.com > To unsubscribe send an email to kernel-leave@mailman.collabora.com
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