Commit 0145e7ac authored by Sam Day's avatar Sam Day Committed by Greg Kroah-Hartman
Browse files

usb: gadget: f_fs: fix DMA-BUF OUT queues 



Currently, DMA_FROM_DEVICE is used when attaching DMABUFs to IN
endpoints and DMA_TO_DEVICE for OUT endpoints. This is inverted from
how it should be.

The result is IOMMU read-only mappings placed on OUT queues,
triggering arm-smmu write faults.

Put differently, OUT endpoints flow data from host -> gadget, meaning
the UDC peripheral needs to have write access to the buffer to fill it
with the incoming data.

This commit flips the directions and updates the implicit-sync helpers
so IN endpoints act as readers and OUT endpoints as writers.

Signed-off-by: default avatarSam Day <me@samcday.com>
Tested-by: David Heidelberg <david@ixit.cz>  # OnePlus 6T on sdm845-next-20251119
Link: https://patch.msgid.link/20260108-ffs-dmabuf-ioctl-fix-v1-2-e51633891a81@samcday.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8e4c1d06

drivers/usb/gadget/function/f_fs.c

+3 −3
Original line number Diff line number Diff line
@@ -1513,7 +1513,7 @@ static int ffs_dmabuf_attach(struct file *file, int fd) 
		goto err_dmabuf_detach;

	}



	dir = epfile->in ? DMA_FROM_DEVICE : DMA_TO_DEVICE;

	dir = epfile->in ? DMA_TO_DEVICE : DMA_FROM_DEVICE;



	err = ffs_dma_resv_lock(dmabuf, nonblock);

	if (err)
@@ -1643,7 +1643,7 @@ static int ffs_dmabuf_transfer(struct file *file, 
	/* Make sure we don't have writers */

	timeout = nonblock ? 0 : msecs_to_jiffies(DMABUF_ENQUEUE_TIMEOUT_MS);

	retl = dma_resv_wait_timeout(dmabuf->resv,

				     dma_resv_usage_rw(epfile->in),

				     dma_resv_usage_rw(!epfile->in),

				     true, timeout);

	if (retl == 0)

		retl = -EBUSY;
@@ -1688,7 +1688,7 @@ static int ffs_dmabuf_transfer(struct file *file, 
	dma_fence_init(&fence->base, &ffs_dmabuf_fence_ops,

		       &priv->lock, priv->context, seqno);



	resv_dir = epfile->in ? DMA_RESV_USAGE_WRITE : DMA_RESV_USAGE_READ;

	resv_dir = epfile->in ? DMA_RESV_USAGE_READ : DMA_RESV_USAGE_WRITE;



	dma_resv_add_fence(dmabuf->resv, &fence->base, resv_dir);

	dma_resv_unlock(dmabuf->resv);