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    SubjectRe: [RFC 3/5] media: v4l2-ctrls: Add support for V4L2_CID_LOCATION
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    On 8/15/19 3:50 PM, Jacopo Mondi wrote:
    > 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@jmondi.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)

    No, these are bitmasks for bitmask controls. So one or more
    status/lock bits can be 1.

    Regards,

    Hans

    >
    > 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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