On 01/20/15 10:24, Florian Echtler wrote: > Hello Hans, > > On 19.01.2015 11:38, Hans Verkuil wrote: >> Sorry for the delay. > No problem, thanks for your feedback. > >>> Note: I'm intentionally using dma-contig instead of vmalloc, as the USB >>> core apparently _will_ try to use DMA for larger bulk transfers. >> As far as I can tell from looking through the usb core code it supports >> scatter-gather DMA, so you should at least use dma-sg rather than dma-contig. >> Physically contiguous memory should always be avoided. > OK, will this work transparently (i.e. just switch from *-contig-* to > *-sg-*)? If not, can you suggest an example driver to use as template? Yes, that should pretty much be seamless. BTW, the more I think about it, the more I am convinced that DMA will also be used by the USB core when you use videobuf2-vmalloc. I've CC-ed Laurent, I think he knows a lot more about this than I do. Laurent, when does the USB core use DMA? What do you need to do on the driver side to have USB use DMA when doing bulk transfers? > >> I'm also missing a patch for the Kconfig that adds a dependency on MEDIA_USB_SUPPORT >> and that selects VIDEOBUF2_DMA_SG. > > Good point, will add that. > >>> +err_unreg_video: >>> + video_unregister_device(&sur40->vdev); >>> +err_unreg_v4l2: >>> + v4l2_device_unregister(&sur40->v4l2); >>> err_free_buffer: >>> kfree(sur40->bulk_in_buffer); >>> err_free_polldev: >>> @@ -436,6 +604,10 @@ static void sur40_disconnect(struct usb_interface *interface) >> >> Is this a hardwired device or hotpluggable? If it is hardwired, then this code is >> OK, but if it is hotpluggable, then this isn't good enough. > > It's hardwired. Out of curiosity, what would I have to change for a > hotpluggable one? In that case you can't clean everything up since some application might still have a filehandle open. You have to wait until the very last filehandle is closed. > >>> + i->type = V4L2_INPUT_TYPE_CAMERA; >>> + i->std = V4L2_STD_UNKNOWN; >>> + strlcpy(i->name, "In-Cell Sensor", sizeof(i->name)); > >> Perhaps just say "Sensor" here? I'm not sure what "In-Cell" means. > > In-cell is referring to the concept of integrating sensor pixels > directly with LCD pixels, I think it's what Samsung calls it. > > Thanks & best regards, Florian > Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
