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Message-ID: <20230416153046.106de4a1@jic23-huawei>
Date: Sun, 16 Apr 2023 15:30:46 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Paul Cercueil <paul@...pouillou.net>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
Vinod Koul <vkoul@...nel.org>,
Michael Hennerich <Michael.Hennerich@...log.com>,
Nuno Sá <noname.nuno@...il.com>,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
linux-iio@...r.kernel.org, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
Alexandru Ardelean <ardeleanalex@...il.com>
Subject: Re: [PATCH v3 04/11] iio: buffer-dma: Enable buffer write support
On Mon, 3 Apr 2023 17:47:53 +0200
Paul Cercueil <paul@...pouillou.net> wrote:
> Adding write support to the buffer-dma code is easy - the write()
> function basically needs to do the exact same thing as the read()
> function: dequeue a block, read or write the data, enqueue the block
> when entirely processed.
>
> Therefore, the iio_buffer_dma_read() and the new iio_buffer_dma_write()
> now both call a function iio_buffer_dma_io(), which will perform this
> task.
>
> The .space_available() callback can return the exact same value as the
> .data_available() callback for input buffers, since in both cases we
> count the exact same thing (the number of bytes in each available
> block).
As they are doing the same thing, I'd like that to be visible down
where the callback is set. As such, do we need a wrapper to
provide the space available version? Perhaps just give the
data_available version a more generic name to make it seem
appropriate for both usecases?
Otherwise LGTM.
Jonathan
>
> Note that we preemptively reset block->bytes_used to the buffer's size
> in iio_dma_buffer_request_update(), as in the future the
> iio_dma_buffer_enqueue() function won't reset it.
>
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> Reviewed-by: Alexandru Ardelean <ardeleanalex@...il.com>
>
> ---
> v2: - Fix block->state not being reset in
> iio_dma_buffer_request_update() for output buffers.
> - Only update block->bytes_used once and add a comment about why we
> update it.
> - Add a comment about why we're setting a different state for output
> buffers in iio_dma_buffer_request_update()
> - Remove useless cast to bool (!!) in iio_dma_buffer_io()
>
> v3: - Reorganize arguments to iio_dma_buffer_io()
> - Change 'is_write' argument to 'is_from_user'
> - Change (__force char *) to (__force __user char *), in
> iio_dma_buffer_write(), since we only want to drop the "const".
> ---
> drivers/iio/buffer/industrialio-buffer-dma.c | 89 ++++++++++++++++----
> include/linux/iio/buffer-dma.h | 7 ++
> 2 files changed, 80 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
> index 1fc91467d1aa..86eced458236 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dma.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dma.c
> @@ -195,6 +195,18 @@ static void _iio_dma_buffer_block_done(struct iio_dma_buffer_block *block)
> block->state = IIO_BLOCK_STATE_DONE;
> }
>
> +static void iio_dma_buffer_queue_wake(struct iio_dma_buffer_queue *queue)
> +{
> + __poll_t flags;
> +
> + if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN)
> + flags = EPOLLIN | EPOLLRDNORM;
> + else
> + flags = EPOLLOUT | EPOLLWRNORM;
> +
> + wake_up_interruptible_poll(&queue->buffer.pollq, flags);
> +}
> +
> /**
> * iio_dma_buffer_block_done() - Indicate that a block has been completed
> * @block: The completed block
> @@ -212,7 +224,7 @@ void iio_dma_buffer_block_done(struct iio_dma_buffer_block *block)
> spin_unlock_irqrestore(&queue->list_lock, flags);
>
> iio_buffer_block_put_atomic(block);
> - wake_up_interruptible_poll(&queue->buffer.pollq, EPOLLIN | EPOLLRDNORM);
> + iio_dma_buffer_queue_wake(queue);
> }
> EXPORT_SYMBOL_GPL(iio_dma_buffer_block_done);
>
> @@ -241,7 +253,7 @@ void iio_dma_buffer_block_list_abort(struct iio_dma_buffer_queue *queue,
> }
> spin_unlock_irqrestore(&queue->list_lock, flags);
>
> - wake_up_interruptible_poll(&queue->buffer.pollq, EPOLLIN | EPOLLRDNORM);
> + iio_dma_buffer_queue_wake(queue);
> }
> EXPORT_SYMBOL_GPL(iio_dma_buffer_block_list_abort);
>
> @@ -335,8 +347,24 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
> queue->fileio.blocks[i] = block;
> }
>
> - block->state = IIO_BLOCK_STATE_QUEUED;
> - list_add_tail(&block->head, &queue->incoming);
> + /*
> + * block->bytes_used may have been modified previously, e.g. by
> + * iio_dma_buffer_block_list_abort(). Reset it here to the
> + * block's so that iio_dma_buffer_io() will work.
> + */
> + block->bytes_used = block->size;
> +
> + /*
> + * If it's an input buffer, mark the block as queued, and
> + * iio_dma_buffer_enable() will submit it. Otherwise mark it as
> + * done, which means it's ready to be dequeued.
> + */
> + if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN) {
> + block->state = IIO_BLOCK_STATE_QUEUED;
> + list_add_tail(&block->head, &queue->incoming);
> + } else {
> + block->state = IIO_BLOCK_STATE_DONE;
> + }
> }
>
> out_unlock:
> @@ -465,20 +493,12 @@ static struct iio_dma_buffer_block *iio_dma_buffer_dequeue(
> return block;
> }
>
> -/**
> - * iio_dma_buffer_read() - DMA buffer read callback
> - * @buffer: Buffer to read form
> - * @n: Number of bytes to read
> - * @user_buffer: Userspace buffer to copy the data to
> - *
> - * Should be used as the read callback for iio_buffer_access_ops
> - * struct for DMA buffers.
> - */
> -int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
> - char __user *user_buffer)
> +static int iio_dma_buffer_io(struct iio_buffer *buffer, size_t n,
> + char __user *user_buffer, bool is_from_user)
> {
> struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
> struct iio_dma_buffer_block *block;
> + void *addr;
> int ret;
>
> if (n < buffer->bytes_per_datum)
> @@ -501,8 +521,13 @@ int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
> n = rounddown(n, buffer->bytes_per_datum);
> if (n > block->bytes_used - queue->fileio.pos)
> n = block->bytes_used - queue->fileio.pos;
> + addr = block->vaddr + queue->fileio.pos;
>
> - if (copy_to_user(user_buffer, block->vaddr + queue->fileio.pos, n)) {
> + if (is_from_user)
> + ret = copy_from_user(addr, user_buffer, n);
> + else
> + ret = copy_to_user(user_buffer, addr, n);
> + if (ret) {
> ret = -EFAULT;
> goto out_unlock;
> }
> @@ -521,8 +546,40 @@ int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
>
> return ret;
> }
> +
> +/**
> + * iio_dma_buffer_read() - DMA buffer read callback
> + * @buffer: Buffer to read form
> + * @n: Number of bytes to read
> + * @user_buffer: Userspace buffer to copy the data to
> + *
> + * Should be used as the read callback for iio_buffer_access_ops
> + * struct for DMA buffers.
> + */
> +int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
> + char __user *user_buffer)
> +{
> + return iio_dma_buffer_io(buffer, n, user_buffer, false);
> +}
> EXPORT_SYMBOL_GPL(iio_dma_buffer_read);
>
> +/**
> + * iio_dma_buffer_write() - DMA buffer write callback
> + * @buffer: Buffer to read form
> + * @n: Number of bytes to read
> + * @user_buffer: Userspace buffer to copy the data from
> + *
> + * Should be used as the write callback for iio_buffer_access_ops
> + * struct for DMA buffers.
> + */
> +int iio_dma_buffer_write(struct iio_buffer *buffer, size_t n,
> + const char __user *user_buffer)
> +{
> + return iio_dma_buffer_io(buffer, n,
> + (__force __user char *)user_buffer, true);
> +}
> +EXPORT_SYMBOL_GPL(iio_dma_buffer_write);
> +
> /**
> * iio_dma_buffer_data_available() - DMA buffer data_available callback
> * @buf: Buffer to check for data availability
> diff --git a/include/linux/iio/buffer-dma.h b/include/linux/iio/buffer-dma.h
> index 18d3702fa95d..490b93f76fa8 100644
> --- a/include/linux/iio/buffer-dma.h
> +++ b/include/linux/iio/buffer-dma.h
> @@ -132,6 +132,8 @@ int iio_dma_buffer_disable(struct iio_buffer *buffer,
> struct iio_dev *indio_dev);
> int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
> char __user *user_buffer);
> +int iio_dma_buffer_write(struct iio_buffer *buffer, size_t n,
> + const char __user *user_buffer);
> size_t iio_dma_buffer_data_available(struct iio_buffer *buffer);
> int iio_dma_buffer_set_bytes_per_datum(struct iio_buffer *buffer, size_t bpd);
> int iio_dma_buffer_set_length(struct iio_buffer *buffer, unsigned int length);
> @@ -142,4 +144,9 @@ int iio_dma_buffer_init(struct iio_dma_buffer_queue *queue,
> void iio_dma_buffer_exit(struct iio_dma_buffer_queue *queue);
> void iio_dma_buffer_release(struct iio_dma_buffer_queue *queue);
>
> +static inline size_t iio_dma_buffer_space_available(struct iio_buffer *buffer)
> +{
> + return iio_dma_buffer_data_available(buffer);
As mentioned above, I don't see having this trivial wrapper as beneficial.
> +}
> +
> #endif
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