linux-kernel - Re: [RFC 3/5] media: v4l2-ctrls: Add support for V4L2_CID

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Message-ID: <20190815135004.7o57rff4ce5sb5bb@uno.localdomain>
Date:   Thu, 15 Aug 2019 15:50:04 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "open list:MEDIA INPUT INFRASTRUCTURE (V4L/DVB)" 
        <linux-media@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 3/5] media: v4l2-ctrls: Add support for V4L2_CID_LOCATION

Hi Hans,

On Thu, Aug 15, 2019 at 03:41:53PM +0200, Hans Verkuil wrote:
> On 8/15/19 3:02 PM, Jacopo Mondi wrote:
> > Hi Laurent,
> >
> > On Thu, Aug 15, 2019 at 01:53:53AM +0300, Laurent Pinchart wrote:
> >> Hi Jacopo,
> >>
> >> Thank you for the patch.
> >>
> >> On Wed, Aug 14, 2019 at 10:28:13PM +0200, Jacopo Mondi wrote:
> >>> Add support for the newly defined V4L2_CID_LOCATION read-only control
> >>> used to report the camera device mounting position.
> >>>
> >>> Signed-off-by: Jacopo Mondi <jacopo@...ndi.org>
> >>> ---
> >>>  drivers/media/v4l2-core/v4l2-ctrls.c | 7 +++++++
> >>>  include/uapi/linux/v4l2-controls.h   | 4 ++++
> >>>  2 files changed, 11 insertions(+)
> >>>
> >>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> >>> index 7d3a33258748..8ab0857df59a 100644
> >>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> >>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> >>> @@ -943,6 +943,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> >>>  	case V4L2_CID_AUTO_FOCUS_RANGE:		return "Auto Focus, Range";
> >>>  	case V4L2_CID_PAN_SPEED:		return "Pan, Speed";
> >>>  	case V4L2_CID_TILT_SPEED:		return "Tilt, Speed";
> >>> +	case V4L2_CID_LOCATION:			return "Location";
> >>
> >> Depending on what we decide to name the control (see review of 2/5), you
> >> should adjust the description accordingly.
> >>
> >>>
> >>>  	/* FM Radio Modulator controls */
> >>>  	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
> >>> @@ -1300,6 +1301,12 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
> >>>  		break;
> >>>  	case V4L2_CID_MPEG_VIDEO_FWHT_PARAMS:
> >>>  		*type = V4L2_CTRL_TYPE_FWHT_PARAMS;
> >>> +	case V4L2_CID_LOCATION:
> >>> +		*type = V4L2_CTRL_TYPE_INTEGER;
> >>> +		*flags |= V4L2_CTRL_FLAG_READ_ONLY;
> >>> +		*min = V4L2_LOCATION_FRONT;
> >>> +		*max = V4L2_LOCATION_BACK;
> >>
> >> I don't think the control should have a min and a max different than the
> >> current value, as it's a fully static control. I'd drop those two lines
> >> here, and drivers will have to set value = min = max = V4L2_LOCATION_xxx
> >> when creating the control. That why you should be able to collapse this
> >> with V4L2_CID_MIN_BUFFERS_FOR_OUTPUT.
> >>
> >
> > Ah, I thought min/max should report the actual control values limits.
> > Anyway, if we move this to be an integer menu control with an helper
> > to parse the DT property and register the control on behalf of
> > drivers, this will change.
> >
> >>> +		*step = 1;
> >>>  		break;
> >>>  	default:
> >>>  		*type = V4L2_CTRL_TYPE_INTEGER;
> >>> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> >>> index 37807f23231e..5c4c7b245921 100644
> >>> --- a/include/uapi/linux/v4l2-controls.h
> >>> +++ b/include/uapi/linux/v4l2-controls.h
> >>> @@ -889,6 +889,10 @@ enum v4l2_auto_focus_range {
> >>>  #define V4L2_CID_PAN_SPEED			(V4L2_CID_CAMERA_CLASS_BASE+32)
> >>>  #define V4L2_CID_TILT_SPEED			(V4L2_CID_CAMERA_CLASS_BASE+33)
> >>>
> >>> +#define V4L2_CID_LOCATION			(V4L2_CID_CAMERA_CLASS_BASE+34)
> >>> +#define V4L2_LOCATION_FRONT			(0 << 0)
> >>> +#define V4L2_LOCATION_BACK			(1 << 0)
> >>
> >> Why not just 0 and 1 ?
> >
> > Or why not BIT(). I saw that the (1 << x) style is the mostly used one in
> > this header file when defining macros like this one so I went for
> > consistency with the existing code.
>
> Definitely not right. This is an enumeration, so just number from 0, 1, 2, ...
>
> Nothing to do with bits/bitmasks.

Aren't these enumerations too?

#define V4L2_CID_3A_LOCK			(V4L2_CID_CAMERA_CLASS_BASE+27)
#define V4L2_LOCK_EXPOSURE			(1 << 0)
#define V4L2_LOCK_WHITE_BALANCE			(1 << 1)
#define V4L2_LOCK_FOCUS				(1 << 2)

#define V4L2_CID_AUTO_FOCUS_START		(V4L2_CID_CAMERA_CLASS_BASE+28)
#define V4L2_CID_AUTO_FOCUS_STOP		(V4L2_CID_CAMERA_CLASS_BASE+29)
#define V4L2_CID_AUTO_FOCUS_STATUS		(V4L2_CID_CAMERA_CLASS_BASE+30)
#define V4L2_AUTO_FOCUS_STATUS_IDLE		(0 << 0)
#define V4L2_AUTO_FOCUS_STATUS_BUSY		(1 << 0)
#define V4L2_AUTO_FOCUS_STATUS_REACHED		(1 << 1)
#define V4L2_AUTO_FOCUS_STATUS_FAILED		(1 << 2)

Anyway, I'm happy to change them to plain numbers.

>
> Regards,
>
> 	Hans
>
> >
> >>
> >>> +
> >>>  /* FM Modulator class control IDs */
> >>>
> >>>  #define V4L2_CID_FM_TX_CLASS_BASE		(V4L2_CTRL_CLASS_FM_TX | 0x900)
> >>
> >> --
> >> Regards,
> >>
> >> Laurent Pinchart
>

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