On Fri, Dec 03, 2021 at 01:55:01PM +0100, Greg KH wrote:
On Thu, Dec 02, 2021 at 01:58:52AM +0100, Michael Grzeschik wrote:Preparing the usb request is not very expensive, when using scatter gather. In that case we can even remove the overhead of the extra pump worker and call the pump function directly. Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx> --- drivers/usb/gadget/function/uvc_v4l2.c | 8 +++++-- drivers/usb/gadget/function/uvc_video.c | 28 +++++++++++++++++++------ drivers/usb/gadget/function/uvc_video.h | 2 ++ 3 files changed, 30 insertions(+), 8 deletions(-) diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c index a2c78690c5c288..020b4adc7840e0 100644 --- a/drivers/usb/gadget/function/uvc_v4l2.c +++ b/drivers/usb/gadget/function/uvc_v4l2.c @@ -169,8 +169,12 @@ uvc_v4l2_qbuf(struct file *file, void *fh, struct v4l2_buffer *b) if (ret < 0) return ret; - if (uvc->state == UVC_STATE_STREAMING) - schedule_work(&video->pump); + if (uvc->state == UVC_STATE_STREAMING) { + if (!video->queue.use_sg) + schedule_work(&video->pump); + else + uvcg_video_pump(video);Wouldn't it be easier to understand this if you flip the if test around: if (video->queue.use_sg) uvcg_video_pump(video); else schedule_work(&video->pump); ? Negagive logic is never fun to read...
Yes, you are not wrong.
Also, are you sure that sg really is not expensive on all systems? What did you test this on, and what was the results?
I tested it on an zynqmp arm64 machine. I tried to test the sg case on an 32 bit IMX with chipidea, but the driver was complaining a lot about "not page aligned sg buffers". So if needed, I would first need to find a working machine to compare this with. However I would think that assigning some pointers on a scatterlist instead of doing memcpy of 1024 bytes should be less expensive. Regards, Michael -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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