Hi Christian, Thank you for the patch. On Mon, Jan 23, 2023 at 01:37:56PM +0100, Christian König wrote: > 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@xxxxxxx> > --- > 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); > + Could we avoid having to call this explicitly in drivers, possibly using devres in dma_heap_create_device_link() ? > #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")) I don't think this is the right device. A UVC device is usually a composite USB device with an audio (UAC) function in addition to UVC, and that may require a different heap (at least conceptually). Wouldn't the video_device be a better candidate to expose the link ? This would create a race condition though, as the link will be created after userspace gets notified of the device being available. > + goto error; > + > /* Register the V4L2 device. */ > if (v4l2_device_register(&intf->dev, &dev->vdev) < 0) > goto error; -- Regards, Laurent Pinchart
