Re: [Patch 1/2] media: v4l: ti-vpe: Add CAL v4l2 camera capture driver

Benoit Parrot
2015-09-16T21:22:52Z

Hans,

I am almost done with my review comment but I am stuck here.

Benoit Parrot <bparrot@ti.com> wrote on Tue [2015-Jun-23 14:36:47 -0500]:
> > > +
> > > +static int cal_get_external_info(struct cal_ctx *ctx)
> > > +{
> > > + struct v4l2_ext_control ctrl_ext;
> > > + struct v4l2_ext_controls ctrls_ext;
> > > + int ret;
> > > +
> > > + ctx_dbg(3, ctx, "%s\n", __func__);
> > > +
> > > + memset(&ctrls_ext, 0, sizeof(ctrls_ext));
> > > + memset(&ctrl_ext, 0, sizeof(ctrl_ext));
> > > +
> > > + ctrl_ext.id = V4L2_CID_PIXEL_RATE;
> > > +
> > > + ctrls_ext.count = 1;
> > > + ctrls_ext.controls = &ctrl_ext;
> > > +
> > > + ret = v4l2_g_ext_ctrls(&ctx->ctrl_handler, &ctrls_ext);
> >
> > Use v4l2_ctrl_g_ctrl_int64() instead: much simpler. You do need to store the
> > v4l2_ctrl pointer for the pixel rate control when you create it, but that's no
> > problem. (or use v4l2_ctrl_find, but I prefer to just cache the pointer).
>
> Hmm, that's how I had it in our local 3.14 branch originally but I kept
> getting 0 instead of the actual pixel rate.
> I'll revert it back and test again against linux-media/master.
>
> >
> > > + if (ret < 0) {
> > > + ctx_err(ctx, "no pixel rate control in subdev: %s\n",
> > > + ctx->sensor->name);
> > > + return -EPIPE;
> > > + }
> > > +
> > > + ctx->external_rate = ctrl_ext.value64;
> > > + ctx_dbg(3, ctx, "sensor Pixel Rate: %d\n", ctx->external_rate);
> > > +
> > > + return 0;
> > > +}

Alright, in order to comply with this comment I rewrote the above function
as follows:

static int cal_get_external_info(struct cal_ctx *ctx)
{
struct v4l2_ctrl *ctrl;
s64 val;
ctx_dbg(3, ctx, "%s\n", __func__);

ctrl = v4l2_ctrl_find(&ctx->ctrl_handler, V4L2_CID_PIXEL_RATE);
// ctrl = v4l2_ctrl_find(ctx->sensor->ctrl_handler, V4L2_CID_PIXEL_RATE);
if (ctrl == NULL) {
ctx_err(ctx, "no pixel rate control in subdev: %s\n",
ctx->sensor->name);
return -EPIPE;
}

// ctx->external_rate = v4l2_ctrl_g_ctrl_int64(ctrl);
val = v4l2_ctrl_g_ctrl_int64(ctrl);
ctx_dbg(3, ctx, "sensor Pixel Rate: s64 %lld\n", val);
ctx->external_rate = (unsigned int)val;
ctx_dbg(3, ctx, "sensor Pixel Rate: %d\n", ctx->external_rate);

return 0;
}

But in all cases the value I get from v4l2_ctrl_g_ctrl_int64 is always zero!
Now I have tripple check with debug code that the subdev is in fact setting
the p_cur and p_new value to something useful (i.e. not 0).

I have traced it down to the get_ctrl() call inside of v4l2_ctrl_g_ctrl_int64.

static int get_ctrl(struct v4l2_ctrl *ctrl, struct v4l2_ext_control *c)
{
struct v4l2_ctrl *master = ctrl->cluster[0];
int ret = 0;
int i;

printk("BENOIT: ==> get_ctrl: ctrl name:%s cur: %lld new: %lld\n",
ctrl->name, *ctrl->p_cur.p_s64, *ctrl->p_new.p_s64);
/* Compound controls are not supported. The new_to_user() and
* cur_to_user() calls below would need to be modified not to access
* userspace memory when called from get_ctrl().
*/
printk("BENOIT: ==> get_ctrl: ctrl name:%s is_int: %d\n", ctrl->name, ctrl->is_int);
if (!ctrl->is_int)
return -EINVAL;

**** It always exits here, because for int64_integer the is_int is not set!
**** which means on the way back out the value reported will always be 0!

printk("BENOIT: ==> get_ctrl: ctrl name:%s flags: 0x%08lx\n", ctrl->name, ctrl->flags);
if (ctrl->flags & V4L2_CTRL_FLAG_WRITE_ONLY)
return -EACCES;

printk("BENOIT: ==> get_ctrl: ctrl name:%s before ctrl_lock:\n", ctrl->name);
v4l2_ctrl_lock(master);
/* g_volatile_ctrl will update the current control values */
if (ctrl->flags & V4L2_CTRL_FLAG_VOLATILE) {
for (i = 0; i < master->ncontrols; i++)
cur_to_new(master->cluster[i]);
ret = call_op(master, g_volatile_ctrl);
new_to_user(c, ctrl);
} else {
cur_to_user(c, ctrl);
}
printk("BENOIT: <== get_ctrl: ctrl name:%s cur: %lld new: %lld\n",
ctrl->name, *ctrl->p_cur.p_s64, *ctrl->p_new.p_s64);
v4l2_ctrl_unlock(master);
return ret;
}

As anyone ever used this successfully to read a V4L2_CID_PIXEL_RATE control value?

Regards,
Benoit