On Wed, Jan 16, 2019 at 7:24 AM Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx> wrote: > > Em Wed, 16 Jan 2019 13:23:10 +0800 > james.hilliard1@xxxxxxxxx escreveu: > > > From: James Hilliard <james.hilliard1@xxxxxxxxx> > > > > Some older systems don't seem to have V4L2_CTRL_WHICH_CUR_VAL so add a > > fallback. > > Nice catch. > > > > > Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx> > > --- > > zbar/video/v4l2.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/zbar/video/v4l2.c b/zbar/video/v4l2.c > > index 0147cb1..b883ecc 100644 > > --- a/zbar/video/v4l2.c > > +++ b/zbar/video/v4l2.c > > @@ -866,7 +866,11 @@ static int v4l2_s_control(zbar_video_t *vdo, > > > > memset(&ctrls, 0, sizeof(ctrls)); > > ctrls.count = 1; > > +#ifdef V4L2_CTRL_WHICH_CUR_VAL > > ctrls.which = V4L2_CTRL_WHICH_CUR_VAL; > > +#else > > + ctrls.ctrl_class = V4L2_CTRL_CLASS_USER; > > +#endif > > ctrls.controls = &c; > > > > memset(&c, 0, sizeof(c)); > > @@ -914,7 +918,11 @@ static int v4l2_g_control(zbar_video_t *vdo, > > > > memset(&ctrls, 0, sizeof(ctrls)); > > ctrls.count = 1; > > +#ifdef V4L2_CTRL_WHICH_CUR_VAL > > ctrls.which = V4L2_CTRL_WHICH_CUR_VAL; > > +#else > > + ctrls.ctrl_class = V4L2_CTRL_CLASS_USER; > > +#endif > > ctrls.controls = &c; > > > > memset(&c, 0, sizeof(c)); > > Hmm... This won't work if the control doesn't belong to V4L2_CTRL_CLASS_USER. > Depending on the device, it may have some controls on different classes. Yeah, I wasn't sure my fix was correct. > > So, it would be better to get the control class from its ID. > > Also, there's still a risk that someone would build zbar against > a Kernel > 4.4, and run it with an older Kernel. > > So, IMHO, the best is to also fill ctrls.which from the control > ID. There is a macro for such purpose. > > As the Kernel keeps backward-compatibility, with this approach, > it should work with any Kernel, even if someone, for example, builds it > on 4.20 and tries to run on a 2.6.x Kernel. > > See the enclosed patch. I tested it here with Kernel 4.20 and works > fine. I'll test it on the system I had which needed the fallback. > > Thanks, > Mauro > > v4l2: add fallback for systems without v4l2_ext_controls which field > > The v4l2_ext_controls.which field was introduced on Kernel 4.4, > in order to solve some ambiguities and make easier to handle > controls. > > Yet, there are several systems running older Kernels. As the > newer Linux Kernels are backward-compatible with the old way, > we can change the logic in a way that would allow someone to > build it against a kernel > 4.4, while letting it to keep running > with legacy Kernels. I needed the fix for a 4.4.0 kernel(ubuntu 16.04). > > Reported-by: James Hilliard <james.hilliard1@xxxxxxxxx> > Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx> > > diff --git a/zbar/video/v4l2.c b/zbar/video/v4l2.c > index 0147cb18d499..0d180947945f 100644 > --- a/zbar/video/v4l2.c > +++ b/zbar/video/v4l2.c > @@ -866,7 +866,11 @@ static int v4l2_s_control(zbar_video_t *vdo, > > memset(&ctrls, 0, sizeof(ctrls)); > ctrls.count = 1; > - ctrls.which = V4L2_CTRL_WHICH_CUR_VAL; > +#ifdef V4L2_CTRL_ID2WHICH > + ctrls.which = V4L2_CTRL_ID2WHICH(p->id); > +#else > + ctrls.ctrl_class = V4L2_CTRL_ID2CLASS(p->id); > +#endif > ctrls.controls = &c; > > memset(&c, 0, sizeof(c)); > @@ -914,7 +918,11 @@ static int v4l2_g_control(zbar_video_t *vdo, > > memset(&ctrls, 0, sizeof(ctrls)); > ctrls.count = 1; > - ctrls.which = V4L2_CTRL_WHICH_CUR_VAL; > +#ifdef V4L2_CTRL_ID2WHICH > + ctrls.which = V4L2_CTRL_ID2WHICH(p->id); > +#else > + ctrls.ctrl_class = V4L2_CTRL_ID2CLASS(p->id); > +#endif > ctrls.controls = &c; > > memset(&c, 0, sizeof(c));
