Le dimanche 09 juin 2024 à 10:53 +0100, Jonathan Cameron a écrit :
On Wed, 5 Jun 2024 13:08:42 +0200 Paul Cercueil paul@crapouillou.net wrote:
Add the necessary infrastructure to the IIO core to support a new optional DMABUF based interface.
With this new interface, DMABUF objects (externally created) can be attached to a IIO buffer, and subsequently used for data transfer.
A userspace application can then use this interface to share DMABUF objects between several interfaces, allowing it to transfer data in a zero-copy fashion, for instance between IIO and the USB stack.
The userspace application can also memory-map the DMABUF objects, and access the sample data directly. The advantage of doing this vs. the read() interface is that it avoids an extra copy of the data between the kernel and userspace. This is particularly userful for high-speed devices which produce several megabytes or even gigabytes of data per second.
As part of the interface, 3 new IOCTLs have been added:
IIO_BUFFER_DMABUF_ATTACH_IOCTL(int fd): Attach the DMABUF object identified by the given file descriptor to the buffer.
IIO_BUFFER_DMABUF_DETACH_IOCTL(int fd): Detach the DMABUF object identified by the given file descriptor from the buffer. Note that closing the IIO buffer's file descriptor will automatically detach all previously attached DMABUF objects.
IIO_BUFFER_DMABUF_ENQUEUE_IOCTL(struct iio_dmabuf *): Request a data transfer to/from the given DMABUF object. Its file descriptor, as well as the transfer size and flags are provided in the "iio_dmabuf" structure.
These three IOCTLs have to be performed on the IIO buffer's file descriptor, obtained using the IIO_BUFFER_GET_FD_IOCTL() ioctl.
Signed-off-by: Paul Cercueil paul@crapouillou.net Signed-off-by: Nuno Sa nuno.sa@analog.com
Need a brief note on the sign off chain. What is Nuno's role in this series as he's not sending the emails and not marked with Co-developed-by
That's a good question. I think he sent one revision of the patchset (v7 or something like that) so he added his SoB.
(Nuno: you confirm?)
I'll add his Co-developed-by then.
Cheers, -Paul
I gave this a much more thorough look in earlier versions than I have today but a few really minor things inline (that I might have fixed up whilst applying) but looks like you'll be done a v11 for Randy's docs comments anyway :(
Jonathan
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index 0138b21b244f..c98c8ac83785 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c
+struct iio_dmabuf_priv {
- struct list_head entry;
- struct kref ref;
- struct iio_buffer *buffer;
- struct iio_dma_buffer_block *block;
- u64 context;
- spinlock_t lock;
Given you are going to have a v11, please add a comment to this lock to say what data it is protecting.
- struct dma_buf_attachment *attach;
- struct sg_table *sgt;
- enum dma_data_direction dir;
- atomic_t seqno;
+};
diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h index 89c3fd7c29ca..1a221c1d7736 100644 --- a/include/linux/iio/buffer_impl.h +++ b/include/linux/iio/buffer_impl.h @@ -9,8 +9,12 @@ #include <uapi/linux/iio/buffer.h> #include <linux/iio/buffer.h> +struct dma_buf_attachment; +struct dma_fence; struct iio_dev; +struct iio_dma_buffer_block; struct iio_buffer; +struct sg_table; /** * INDIO_BUFFER_FLAG_FIXED_WATERMARK - Watermark level of the buffer can not be @@ -39,6 +43,13 @@ struct iio_buffer; * device stops sampling. Calles are balanced with @enable. * @release: called when the last reference to the buffer is dropped, * should free all resources allocated by the buffer.
- @attach_dmabuf: called from userspace via ioctl to attach
one external
DMABUF.
- @detach_dmabuf: called from userspace via ioctl to detach
one previously
attached DMABUF.
- @enqueue_dmabuf: called from userspace via ioctl to queue
this DMABUF
object to this buffer. Requires a validDMABUF fd, that
was previouly attached to this buffer.Missing docs for lock_queue() and unlock_queue()
Kernel-doc must be complete or bots are going to moan at us :(
* @modes: Supported operating modes by this buffer type * @flags: A bitmask combination of INDIO_BUFFER_FLAG_* * @@ -68,6 +79,17 @@ struct iio_buffer_access_funcs { void (*release)(struct iio_buffer *buffer);
- struct iio_dma_buffer_block * (*attach_dmabuf)(struct
iio_buffer *buffer,
structdma_buf_attachment *attach);
- void (*detach_dmabuf)(struct iio_buffer *buffer,
struct iio_dma_buffer_block *block);- int (*enqueue_dmabuf)(struct iio_buffer *buffer,
struct iio_dma_buffer_block *block,struct dma_fence *fence, structsg_table *sgt,
size_t size, bool cyclic);- void (*lock_queue)(struct iio_buffer *buffer);
- void (*unlock_queue)(struct iio_buffer *buffer);