Hi Guennadi,
On Tuesday, 5 December 2017 10:06:02 EET Guennadi Liakhovetski wrote:
> On Tue, 5 Dec 2017, Laurent Pinchart wrote:
> > On Tuesday, 5 December 2017 02:24:30 EET Laurent Pinchart wrote:
> >> On Wednesday, 8 November 2017 18:00:14 EET Guennadi Liakhovetski wrote:
> > [snip]
> >
> >>> +static void uvc_video_decode_meta(struct uvc_streaming *stream,
> >>> + struct uvc_buffer *buf, struct uvc_buffer *meta_buf,
> >>> + u8 *mem, unsigned int length)
> >>
> >> The buf parameter is unused, you can remove it. mem isn't modified, I
> >> would make it const.
> >>
> >>> +{
> >>> + struct uvc_meta_buf *meta;
> >>> + size_t len_std = 2;
> >>> + bool has_pts, has_scr;
> >>> + unsigned long flags;
> >>> + struct timespec ts;
> >>> + u8 *scr;
> >>
> >> And scr should be const too.
> >>
> >>> +
> >>> + if (!meta_buf || length == 2 ||
> >>> + meta_buf->length - meta_buf->bytesused <
> >>> + length + sizeof(meta->ns) + sizeof(meta->sof))
> >>> + return;
> >>
> >> If the metadata buffer overflows should we also set the error bit like
> >> we do for video buffers ? I have mixed feelings about this, I'd
> >> appreciate your input.
> >>
> >>> + has_pts = mem[1] & UVC_STREAM_PTS;
> >>> + has_scr = mem[1] & UVC_STREAM_SCR;
> >>> +
> >>> + if (has_pts) {
> >>> + len_std += 4;
> >>> + scr = mem + 6;
> >>> + } else {
> >>> + scr = mem + 2;
> >>> + }
> >>> +
> >>> + if (has_scr)
> >>> + len_std += 6;
> >>> +
> >>> + if (stream->cur_meta_format == V4L2_META_FMT_UVC)
> >>> + length = len_std;
> >>> +
> >>> + if (length == len_std && (!has_scr ||
> >>> + !memcmp(scr, stream->clock.last_scr, 6)))
> >>> + return;
> >>> +
> >>> + meta = (struct uvc_meta_buf *)((u8 *)meta_buf->mem +
> >>> meta_buf->bytesused);
> >>> + local_irq_save(flags);
> >>> + uvc_video_get_ts(&ts);
> >>
> >> FYI, Arnd has posted https://patchwork.kernel.org/patch/10076887/. If
> >> the patch gets merged first I can help with the rebasing.
> >
> > I've reviewed and merged Arnd patches in my tree, and...
> >
> >>> + meta->sof = usb_get_current_frame_number(stream->dev->udev);
> >>> + local_irq_restore(flags);
> >>> + meta->ns = timespec_to_ns(&ts);
> >>
> >> The meta pointer can be unaligned as the structure is packed and its
> >> size
> >> isn't a multiple of the size of the largest field (and it can contain an
> >> unspecified amount of vendor data anyway). You thus can't access it
> >> directly on all architectures, you will need to use the put_unaligned
> >> macro. As I haven't checked whether all architectures can handle
> >> unaligned accesses without generating a trap, I would store the USB
> >> frame number in a local variable and use the put_unaligned macro output
> >> of the IRQ disabled section (feel free to show me that I'm
> >> unnecessarily cautious :-)).
> >>
> >>> + if (has_scr)
> >>> + memcpy(stream->clock.last_scr, scr, 6);
> >>> +
> >>> + memcpy(&meta->length, mem, length);
> >>> + meta_buf->bytesused += length + sizeof(meta->ns) +
> >>> sizeof(meta->sof);
> >>> +
> >>> + uvc_trace(UVC_TRACE_FRAME,
> >>> + "%s(): t-sys %lu.%09lus, SOF %u, len %u, flags 0x%x, PTS %u,
> >>> STC %u frame SOF %u\n",
> >>> + __func__, ts.tv_sec, ts.tv_nsec, meta->sof,
> >>> + meta->length, meta->flags, has_pts ? *(u32 *)meta->buf : 0,
> >>> + has_scr ? *(u32 *)scr : 0,
> >>> + has_scr ? *(u32 *)(scr + 4) & 0x7ff : 0);
> >>> +}
> >
> > [snip]
> >
> >> For your convenience I've rebased your patch series on top of the two
> >> patches I mentioned and added another patch on top that contains fixes
> >> for all the small issues mentioned above. The result is available at
>
> In your rebased version you've also dropped the hunk for
> drivers/media/v4l2-core/v4l2-ioctl.c adding a description for the new
> V4L2_META_FMT_UVC format - is that on purpose?
Unless I'm mistaken I've moved it to patch 1/3.
> >> git://linuxtv.org/pinchartl/media.git uvc/metadata
> >>
> >> There are just a handful of issues or questions I haven't addressed, if
> >> we handle them I think we'll be good to go.
> >
> > ... updated the above branch with a rebased version of the series.
--
Regards,
Laurent Pinchart
