[PATCH 2/2] media: uvcvideo: expose dma-heap hint to userspace

[Christian König]

Expose an indicator to let userspace know from which dma_heap
to allocate for buffers of this device.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/media/usb/uvc/uvc_driver.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index e4bcb5011360..b247026b68c5 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/atomic.h>
+#include <linux/dma-heap.h>
 #include <linux/gpio/consumer.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
@@ -1909,6 +1910,8 @@ static void uvc_unregister_video(struct uvc_device *dev)
 
 	if (dev->vdev.dev)
 		v4l2_device_unregister(&dev->vdev);
+	dma_heap_remove_device_link(&dev->udev->dev);
+
 #ifdef CONFIG_MEDIA_CONTROLLER
 	if (media_devnode_is_registered(dev->mdev.devnode))
 		media_device_unregister(&dev->mdev);
@@ -2181,6 +2184,14 @@ static int uvc_probe(struct usb_interface *intf,
 			 dev->uvc_version >> 8, dev->uvc_version & 0xff);
 	}
 
+	/*
+	 * UVC exports DMA-buf buffers with dirty CPU caches. For compatibility
+	 * with device which can't snoop the CPU cache it's best practice to
+	 * allocate DMA-bufs from the system DMA-heap.
+	 */
+	if (dma_heap_create_device_link(&dev->udev->dev, "system"))
+		goto error;
+
 	/* Register the V4L2 device. */
 	if (v4l2_device_register(&intf->dev, &dev->vdev) < 0)
 		goto error;
-- 
2.34.1