[PATCH] qcap: fix recent regression that limited Wine's v4l2 support to devices that read()

[Damjan Jovanovic]

On Sat, Apr 20, 2019 at 5:44 PM Zebediah Figura <z.figura12 at gmail.com>
wrote:

> On 4/20/19 10:31 AM, Damjan Jovanovic wrote:
> >
> >
> > On Sat, Apr 20, 2019 at 4:52 PM Zebediah Figura <z.figura12 at gmail.com
> > <mailto:z.figura12 at gmail.com>> wrote:
> >
> >     On 4/20/19 8:15 AM, Damjan Jovanovic wrote:
> >      > Recent changes to qcap/v4l.c resulted in the removal of mmap()
> >      > for v4l2 devices, but read() is optional for device drivers and
> >      > some don't support it. This isn't a major problem with the
> >      > presense of libv4l2 though, as it can emulate read() on top of
> >      > mmap(). However the code checks whether the device can read(),
> >      > and if not, doesn't even try to use it, even though it can.
> >      >
> >      > Fix this by only warning that read() is being emulated, and
> >      > continuing with libv4l2 if available.
> >      >
> >      > Also clarifies the logging.
> >      >
> >      > Signed-off-by: Damjan Jovanovic <damjan.jov at gmail.com
> >     <mailto:damjan.jov at gmail.com>>
> >      > ---
> >      >   dlls/qcap/v4l.c | 13 ++++++++-----
> >      >   1 file changed, 8 insertions(+), 5 deletions(-)
> >      >
> >      >
> >      >
> >
> >     This doesn't seem right; libv4l2 should massage the result of
> >     VIDIOC_QUERYCAP to include V4L2_CAP_READWRITE. See
> >     <
> https://git.linuxtv.org/v4l-utils.git/tree/lib/libv4l2/libv4l2.c#n1210>.
> >
> >
> > On FreeBSD 11.2 with libv4l-1.6.3_4, that is certainly NOT the case. It
> > could be a newer or not yet released feature.
> >
> >
> >
>
> It's been the case since libv4l2 0.5:
> <
> https://git.linuxtv.org/v4l-utils.git/commit/lib/libv4l2/libv4l2.c?id=0215f2ac08c3ad0dc66ad8036f4e186a5e8f56d6
> >
>
> If FreeBSD is using 1.6.3, then I think something else is wrong. Are you
> sure that libv4l2 is actually being loaded?
>
>
int v4l2_ioctl(int fd, unsigned long int request, ...)
{
...
        if (devices[index].convert == NULL)
                goto no_capture_request;

<your code nippet from above>

no_capture_request:



So the code that would set that flag, is skipped if the .convert field is
NULL.

When is it NULL?
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