[v2,03/11] iio: buffer-dma: Enable buffer write support

Commit Message

Nuno Sa April 5, 2024, 3 p.m. UTC

From: Paul Cercueil <[e-mail]>

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.

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 <[e-mail]>
Reviewed-by: Alexandru Ardelean <[e-mail]>
Signed-off-by: Nuno Sa <[e-mail]>
---
 drivers/iio/buffer/industrialio-buffer-dma.c | 89 +++++++++++++++++++++++-----
 include/linux/iio/buffer-dma.h               |  2 +
 2 files changed, 75 insertions(+), 16 deletions(-)

Comments

Jonathan Cameron April 6, 2024, 4:23 p.m. UTC | #1

On Fri, 5 Apr 2024 17:00:01 +0200
Nuno Sa <[e-mail]> wrote:

> From: Paul Cercueil <[e-mail]>
> 
> 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.
> 
> 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 <[e-mail]>
> Reviewed-by: Alexandru Ardelean <[e-mail]>
> Signed-off-by: Nuno Sa <[e-mail]>

One trivial comment on alignment that I noticed whilst reminding
myself of this patch. Otherwise looks good.


> +
> +/**
> + * 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)

Prefer aligning char with after the (

> +{
> +	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);
>

Nuno Sá April 8, 2024, 8:42 a.m. UTC | #2

On Sat, 2024-04-06 at 17:23 +0100, Jonathan Cameron wrote:
> On Fri, 5 Apr 2024 17:00:01 +0200
> Nuno Sa <[e-mail]> wrote:
> 
> > From: Paul Cercueil <[e-mail]>
> > 
> > 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.
> > 
> > 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 <[e-mail]>
> > Reviewed-by: Alexandru Ardelean <[e-mail]>
> > Signed-off-by: Nuno Sa <[e-mail]>
> 
> One trivial comment on alignment that I noticed whilst reminding
> myself of this patch. Otherwise looks good.
> 
> 
> > +
> > +/**
> > + * 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)
> 
> Prefer aligning char with after the (

I was keeping it as it was. But I can fix it up while doing the change, yes.


- Nuno Sá

Patch

diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
index 404f9867bdc5..29cc3083cb7e 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:
@@ -488,20 +516,12 @@  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)
@@ -524,8 +544,13 @@  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;
 	}
@@ -544,8 +569,40 @@  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_usage() - DMA buffer data_available and
  * space_available callback
diff --git a/include/linux/iio/buffer-dma.h b/include/linux/iio/buffer-dma.h
index 52a838ec0e57..6e27e47077d5 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_usage(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);