Re: [PATCH v7 5/7] v4l2-ctrls: add support for V4L2_CTRL_WHICH_MIN/MAX_VAL

Yunke Cao
2022-09-20T10:01:24Z

Hi Laurent, Hans,

Thank you Laurent for the review.

On Thu, Aug 25, 2022 at 1:20 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Yunke and Hans,
>
> Thank you for the patch.
>
> On Tue, Jun 28, 2022 at 04:57:03PM +0900, Yunke Cao wrote:
> > From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> >
> > Add the capability of retrieving the min and max values of a
> > compound control.
> >
> > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> > Signed-off-by: Yunke Cao <yunkec@google.com>
> > ---
> > git am from https://lore.kernel.org/all/20191119113457.57833-3-hverkuil-cisco@xs4all.nl/
> > -Fixed some merge conflits.
> > -Fixed the build error in drivers/media/platform/qcom/venus.
> >
> > .../media/v4l/vidioc-g-ext-ctrls.rst | 7 +-
> > .../media/videodev2.h.rst.exceptions | 2 +
> > drivers/media/i2c/imx214.c | 5 +-
> > .../media/platform/qcom/venus/venc_ctrls.c | 4 +
> > drivers/media/v4l2-core/v4l2-ctrls-api.c | 51 +++++--
> > drivers/media/v4l2-core/v4l2-ctrls-core.c | 135 ++++++++++++++++--
> > drivers/media/v4l2-core/v4l2-ioctl.c | 4 +-
> > include/media/v4l2-ctrls.h | 32 ++++-
> > include/uapi/linux/videodev2.h | 2 +
> > 9 files changed, 214 insertions(+), 28 deletions(-)
> >
> > diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
> > index 7473baa4e977..65a5f878cc28 100644
> > --- a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
> > +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
> > @@ -284,14 +284,17 @@ still cause this situation.
> > - Which value of the control to get/set/try.
> > * - :cspan:`2` ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of
> > the control, ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default
> > + value of the control, ``V4L2_CTRL_WHICH_MIN_VAL`` will return the minimum
> > + value of the control, ``V4L2_CTRL_WHICH_MAX_VAL`` will return the maximum
>
> The concept of minimum and maximum values for compound controls can be
> quite ill-defined. Could we document here that the definition of the
> minimum and maximum values are provided by the control documentation for
> compound controls ?
>

Sure, I can do that.

> > value of the control and ``V4L2_CTRL_WHICH_REQUEST_VAL`` indicates that
> > these controls have to be retrieved from a request or tried/set for
> > a request. In the latter case the ``request_fd`` field contains the
> > file descriptor of the request that should be used. If the device
> > does not support requests, then ``EACCES`` will be returned.
> >
> > - When using ``V4L2_CTRL_WHICH_DEF_VAL`` be aware that you can only
> > - get the default value of the control, you cannot set or try it.
> > + When using ``V4L2_CTRL_WHICH_DEF_VAL``, ``V4L2_CTRL_WHICH_MIN_VAL``
> > + or ``V4L2_CTRL_WHICH_MAX_VAL`` be aware that you can only get the
> > + default/minimum/maximum value of the control, you cannot set or try it.
> >
> > For backwards compatibility you can also use a control class here
> > (see :ref:`ctrl-class`). In that case all controls have to
> > diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > index 7b423475281d..e2dde31d76df 100644
> > --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > @@ -553,6 +553,8 @@ ignore define V4L2_CTRL_DRIVER_PRIV
> > ignore define V4L2_CTRL_MAX_DIMS
> > ignore define V4L2_CTRL_WHICH_CUR_VAL
> > ignore define V4L2_CTRL_WHICH_DEF_VAL
> > +ignore define V4L2_CTRL_WHICH_MIN_VAL
> > +ignore define V4L2_CTRL_WHICH_MAX_VAL
> > ignore define V4L2_CTRL_WHICH_REQUEST_VAL
> > ignore define V4L2_OUT_CAP_CUSTOM_TIMINGS
> > ignore define V4L2_CID_MAX_CTRLS
> > diff --git a/drivers/media/i2c/imx214.c b/drivers/media/i2c/imx214.c
> > index 83c1737abeec..aa0bfd18f7b7 100644
> > --- a/drivers/media/i2c/imx214.c
> > +++ b/drivers/media/i2c/imx214.c
> > @@ -1037,7 +1037,10 @@ static int imx214_probe(struct i2c_client *client)
> > imx214->unit_size = v4l2_ctrl_new_std_compound(&imx214->ctrls,
> > NULL,
> > V4L2_CID_UNIT_CELL_SIZE,
> > - v4l2_ctrl_ptr_create((void *)&unit_size));
> > + v4l2_ctrl_ptr_create((void *)&unit_size),
> > + v4l2_ctrl_ptr_create(NULL),
> > + v4l2_ctrl_ptr_create(NULL));
>
> Would it make sense to set min = max = default for read-only controls ?
> You should also update the documentation of V4L2_CID_UNIT_CELL_SIZE (and
> other controls below) to indicate how their minimum and maximum are
> defined.
>

I only modified imx214.c and venc_ctrls.c to fix the build errors
caused by the change
of v4l2_ctrl_ptr_create().

Can I leave the min/max for these controls undefined in this patch (by
returning error
as we discussed below)?

setting min = max = default for V4L2_CID_UNIT_CELL_SIZE makes sense to me.
I can implement and document V4L2_CID_UNIT_CELL_SIZE in a followup patch.
I'm not familiar with the other two controls though, so I prefer to
leave them undefined.

> > +
> > ret = imx214->ctrls.error;
> > if (ret) {
> > dev_err(&client->dev, "%s control init failed (%d)\n",
> > diff --git a/drivers/media/platform/qcom/venus/venc_ctrls.c b/drivers/media/platform/qcom/venus/venc_ctrls.c
> > index ed44e5800759..4af8f9ca12a6 100644
> > --- a/drivers/media/platform/qcom/venus/venc_ctrls.c
> > +++ b/drivers/media/platform/qcom/venus/venc_ctrls.c
> > @@ -579,10 +579,14 @@ int venc_ctrl_init(struct venus_inst *inst)
> >
> > v4l2_ctrl_new_std_compound(&inst->ctrl_handler, &venc_ctrl_ops,
> > V4L2_CID_COLORIMETRY_HDR10_CLL_INFO,
> > + v4l2_ctrl_ptr_create(NULL),
> > + v4l2_ctrl_ptr_create(NULL),
> > v4l2_ctrl_ptr_create(NULL));
> >
> > v4l2_ctrl_new_std_compound(&inst->ctrl_handler, &venc_ctrl_ops,
> > V4L2_CID_COLORIMETRY_HDR10_MASTERING_DISPLAY,
> > + v4l2_ctrl_ptr_create(NULL),
> > + v4l2_ctrl_ptr_create(NULL),
> > v4l2_ctrl_ptr_create(NULL));
> >
> > v4l2_ctrl_new_std_menu(&inst->ctrl_handler, &venc_ctrl_ops,
> > diff --git a/drivers/media/v4l2-core/v4l2-ctrls-api.c b/drivers/media/v4l2-core/v4l2-ctrls-api.c
> > index db9baa0bd05f..8a9c816b0dab 100644
> > --- a/drivers/media/v4l2-core/v4l2-ctrls-api.c
> > +++ b/drivers/media/v4l2-core/v4l2-ctrls-api.c
> > @@ -97,6 +97,28 @@ static int def_to_user(struct v4l2_ext_control *c, struct v4l2_ctrl *ctrl)
> > return ptr_to_user(c, ctrl, ctrl->p_new);
> > }
> >
> > +/* Helper function: copy the minimum control value back to the caller */
> > +static int min_to_user(struct v4l2_ext_control *c, struct v4l2_ctrl *ctrl)
> > +{
> > + int idx;
> > +
> > + for (idx = 0; idx < ctrl->elems; idx++)
> > + ctrl->type_ops->minimum(ctrl, idx, ctrl->p_new);
> > +
> > + return ptr_to_user(c, ctrl, ctrl->p_new);
> > +}
> > +
> > +/* Helper function: copy the maximum control value back to the caller */
> > +static int max_to_user(struct v4l2_ext_control *c, struct v4l2_ctrl *ctrl)
> > +{
> > + int idx;
> > +
> > + for (idx = 0; idx < ctrl->elems; idx++)
> > + ctrl->type_ops->maximum(ctrl, idx, ctrl->p_new);
> > +
> > + return ptr_to_user(c, ctrl, ctrl->p_new);
> > +}
> > +
> > /* Helper function: copy the caller-provider value to the given control value */
> > static int user_to_ptr(struct v4l2_ext_control *c,
> > struct v4l2_ctrl *ctrl,
> > @@ -220,8 +242,8 @@ static int prepare_ext_ctrls(struct v4l2_ctrl_handler *hdl,
> > cs->error_idx = i;
> >
> > if (cs->which &&
> > - cs->which != V4L2_CTRL_WHICH_DEF_VAL &&
> > - cs->which != V4L2_CTRL_WHICH_REQUEST_VAL &&
> > + (cs->which < V4L2_CTRL_WHICH_DEF_VAL ||
> > + cs->which > V4L2_CTRL_WHICH_MAX_VAL) &&
> > V4L2_CTRL_ID2WHICH(id) != cs->which) {
> > dprintk(vdev,
> > "invalid which 0x%x or control id 0x%x\n",
> > @@ -335,8 +357,8 @@ static int prepare_ext_ctrls(struct v4l2_ctrl_handler *hdl,
> > */
> > static int class_check(struct v4l2_ctrl_handler *hdl, u32 which)
> > {
> > - if (which == 0 || which == V4L2_CTRL_WHICH_DEF_VAL ||
> > - which == V4L2_CTRL_WHICH_REQUEST_VAL)
> > + if (which == 0 || (which >= V4L2_CTRL_WHICH_DEF_VAL &&
> > + which <= V4L2_CTRL_WHICH_MAX_VAL))
> > return 0;
> > return find_ref_lock(hdl, which | 1) ? 0 : -EINVAL;
> > }
> > @@ -356,10 +378,12 @@ int v4l2_g_ext_ctrls_common(struct v4l2_ctrl_handler *hdl,
> > struct v4l2_ctrl_helper *helpers = helper;
> > int ret;
> > int i, j;
> > - bool is_default, is_request;
> > + bool is_default, is_request, is_min, is_max;
> >
> > is_default = (cs->which == V4L2_CTRL_WHICH_DEF_VAL);
> > is_request = (cs->which == V4L2_CTRL_WHICH_REQUEST_VAL);
> > + is_min = (cs->which == V4L2_CTRL_WHICH_MIN_VAL);
> > + is_max = (cs->which == V4L2_CTRL_WHICH_MAX_VAL);
> >
> > cs->error_idx = cs->count;
> > cs->which = V4L2_CTRL_ID2WHICH(cs->which);
> > @@ -399,13 +423,14 @@ int v4l2_g_ext_ctrls_common(struct v4l2_ctrl_handler *hdl,
> >
> > /*
> > * g_volatile_ctrl will update the new control values.
> > - * This makes no sense for V4L2_CTRL_WHICH_DEF_VAL and
> > + * This makes no sense for V4L2_CTRL_WHICH_DEF_VAL,
> > + * V4L2_CTRL_WHICH_MIN_VAL, V4L2_CTRL_WHICH_MAX_VAL and
> > * V4L2_CTRL_WHICH_REQUEST_VAL. In the case of requests
> > * it is v4l2_ctrl_request_complete() that copies the
> > * volatile controls at the time of request completion
> > * to the request, so you don't want to do that again.
> > */
> > - if (!is_default && !is_request &&
> > + if (!is_default && !is_request && !is_min && !is_max &&
> > ((master->flags & V4L2_CTRL_FLAG_VOLATILE) ||
> > (master->has_volatiles && !is_cur_manual(master)))) {
> > for (j = 0; j < master->ncontrols; j++)
> > @@ -432,6 +457,10 @@ int v4l2_g_ext_ctrls_common(struct v4l2_ctrl_handler *hdl,
> > ret = def_to_user(cs->controls + idx, ref->ctrl);
> > else if (is_request && ref->valid_p_req)
> > ret = req_to_user(cs->controls + idx, ref);
> > + else if (is_min)
> > + ret = min_to_user(cs->controls + idx, ref->ctrl);
> > + else if (is_max)
> > + ret = max_to_user(cs->controls + idx, ref->ctrl);
> > else if (is_volatile)
> > ret = new_to_user(cs->controls + idx, ref->ctrl);
> > else
> > @@ -523,9 +552,11 @@ int try_set_ext_ctrls_common(struct v4l2_fh *fh,
> >
> > cs->error_idx = cs->count;
> >
> > - /* Default value cannot be changed */
> > - if (cs->which == V4L2_CTRL_WHICH_DEF_VAL) {
> > - dprintk(vdev, "%s: cannot change default value\n",
> > + /* Default/minimum/maximum values cannot be changed */
> > + if (cs->which == V4L2_CTRL_WHICH_DEF_VAL ||
> > + cs->which == V4L2_CTRL_WHICH_MIN_VAL ||
> > + cs->which == V4L2_CTRL_WHICH_MAX_VAL) {
> > + dprintk(vdev, "%s: cannot change default/min/max value\n",
> > video_device_node_name(vdev));
> > return -EINVAL;
> > }
> > diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
> > index 35d43ba650db..8c5828c7c6d3 100644
> > --- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
> > +++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
> > @@ -186,6 +186,28 @@ static void std_init_compound(const struct v4l2_ctrl *ctrl, u32 idx,
> > }
> > }
> >
> > +static void std_min_compound(const struct v4l2_ctrl *ctrl, u32 idx,
> > + union v4l2_ctrl_ptr ptr)
> > +{
> > + void *p = ptr.p + idx * ctrl->elem_size;
> > +
> > + if (ctrl->p_min.p_const)
> > + memcpy(p, ctrl->p_min.p_const, ctrl->elem_size);
> > + else
> > + memset(p, 0, ctrl->elem_size);
> > +}
> > +
> > +static void std_max_compound(const struct v4l2_ctrl *ctrl, u32 idx,
> > + union v4l2_ctrl_ptr ptr)
> > +{
> > + void *p = ptr.p + idx * ctrl->elem_size;
> > +
> > + if (ctrl->p_max.p_const)
> > + memcpy(p, ctrl->p_max.p_const, ctrl->elem_size);
> > + else
> > + memset(p, 0, ctrl->elem_size);
> > +}
> > +
> > static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> > union v4l2_ctrl_ptr ptr)
> > {
> > @@ -224,6 +246,82 @@ static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
> > }
> > }
> >
> > +static void std_minimum(const struct v4l2_ctrl *ctrl, u32 idx,
> > + union v4l2_ctrl_ptr ptr)
> > +{
> > + switch (ctrl->type) {
> > + case V4L2_CTRL_TYPE_STRING:
> > + idx *= ctrl->elem_size;
> > + memset(ptr.p_char + idx, ' ', ctrl->minimum);
> > + ptr.p_char[idx + ctrl->minimum] = '\0';
> > + break;
> > + case V4L2_CTRL_TYPE_INTEGER64:
> > + ptr.p_s64[idx] = ctrl->minimum;
> > + break;
> > + case V4L2_CTRL_TYPE_INTEGER:
> > + case V4L2_CTRL_TYPE_INTEGER_MENU:
> > + case V4L2_CTRL_TYPE_MENU:
> > + case V4L2_CTRL_TYPE_BITMASK:
> > + case V4L2_CTRL_TYPE_BOOLEAN:
> > + ptr.p_s32[idx] = ctrl->minimum;
> > + break;
> > + case V4L2_CTRL_TYPE_BUTTON:
> > + case V4L2_CTRL_TYPE_CTRL_CLASS:
> > + ptr.p_s32[idx] = 0;
> > + break;
> > + case V4L2_CTRL_TYPE_U8:
> > + ptr.p_u8[idx] = ctrl->minimum;
> > + break;
> > + case V4L2_CTRL_TYPE_U16:
> > + ptr.p_u16[idx] = ctrl->minimum;
> > + break;
> > + case V4L2_CTRL_TYPE_U32:
> > + ptr.p_u32[idx] = ctrl->minimum;
> > + break;
> > + default:
> > + std_min_compound(ctrl, idx, ptr);
> > + break;
> > + }
> > +}
> > +
> > +static void std_maximum(const struct v4l2_ctrl *ctrl, u32 idx,
> > + union v4l2_ctrl_ptr ptr)
> > +{
> > + switch (ctrl->type) {
> > + case V4L2_CTRL_TYPE_STRING:
> > + idx *= ctrl->elem_size;
> > + memset(ptr.p_char + idx, ' ', ctrl->maximum);
> > + ptr.p_char[idx + ctrl->maximum] = '\0';
> > + break;
> > + case V4L2_CTRL_TYPE_INTEGER64:
> > + ptr.p_s64[idx] = ctrl->maximum;
> > + break;
> > + case V4L2_CTRL_TYPE_INTEGER:
> > + case V4L2_CTRL_TYPE_INTEGER_MENU:
> > + case V4L2_CTRL_TYPE_MENU:
> > + case V4L2_CTRL_TYPE_BITMASK:
> > + case V4L2_CTRL_TYPE_BOOLEAN:
> > + ptr.p_s32[idx] = ctrl->maximum;
> > + break;
> > + case V4L2_CTRL_TYPE_BUTTON:
> > + case V4L2_CTRL_TYPE_CTRL_CLASS:
> > + ptr.p_s32[idx] = 0;
> > + break;
> > + case V4L2_CTRL_TYPE_U8:
> > + ptr.p_u8[idx] = ctrl->maximum;
> > + break;
> > + case V4L2_CTRL_TYPE_U16:
> > + ptr.p_u16[idx] = ctrl->maximum;
> > + break;
> > + case V4L2_CTRL_TYPE_U32:
> > + ptr.p_u32[idx] = ctrl->maximum;
> > + break;
> > + default:
> > + std_max_compound(ctrl, idx, ptr);
> > + break;
> > + }
> > +}
> > +
> > static void std_log(const struct v4l2_ctrl *ctrl)
> > {
> > union v4l2_ctrl_ptr ptr = ctrl->p_cur;
> > @@ -986,6 +1084,8 @@ static int std_validate(const struct v4l2_ctrl *ctrl, u32 idx,
> > static const struct v4l2_ctrl_type_ops std_type_ops = {
> > .equal = std_equal,
> > .init = std_init,
> > + .minimum = std_minimum,
> > + .maximum = std_maximum,
> > .log = std_log,
> > .validate = std_validate,
> > };
> > @@ -1368,7 +1468,10 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
> > s64 min, s64 max, u64 step, s64 def,
> > const u32 dims[V4L2_CTRL_MAX_DIMS], u32 elem_size,
> > u32 flags, const char * const *qmenu,
> > - const s64 *qmenu_int, const union v4l2_ctrl_ptr p_def,
> > + const s64 *qmenu_int,
> > + const union v4l2_ctrl_ptr p_def,
> > + const union v4l2_ctrl_ptr p_min,
> > + const union v4l2_ctrl_ptr p_max,
> > void *priv)
> > {
> > struct v4l2_ctrl *ctrl;
> > @@ -1515,7 +1618,7 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
> > sz_extra += 2 * tot_ctrl_size;
> >
> > if (type >= V4L2_CTRL_COMPOUND_TYPES && p_def.p_const)
> > - sz_extra += elem_size;
> > + sz_extra += elem_size * 3;
> >
> > ctrl = kvzalloc(sizeof(*ctrl) + sz_extra, GFP_KERNEL);
> > if (ctrl == NULL) {
> > @@ -1565,6 +1668,13 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
> > ctrl->p_def.p = ctrl->p_cur.p + tot_ctrl_size;
> > memcpy(ctrl->p_def.p, p_def.p_const, elem_size);
> > }
> > + if (type >= V4L2_CTRL_COMPOUND_TYPES &&
> > + p_min.p_const && p_max.p_const) {
> > + ctrl->p_min.p = ctrl->p_cur.p + 2 * tot_ctrl_size;
> > + memcpy(ctrl->p_min.p, p_min.p_const, elem_size);
> > + ctrl->p_max.p = ctrl->p_cur.p + 3 * tot_ctrl_size;
> > + memcpy(ctrl->p_max.p, p_max.p_const, elem_size);
> > + }
> >
> > for (idx = 0; idx < elems; idx++) {
> > ctrl->type_ops->init(ctrl, idx, ctrl->p_cur);
> > @@ -1617,7 +1727,8 @@ struct v4l2_ctrl *v4l2_ctrl_new_custom(struct v4l2_ctrl_handler *hdl,
> > type, min, max,
> > is_menu ? cfg->menu_skip_mask : step, def,
> > cfg->dims, cfg->elem_size,
> > - flags, qmenu, qmenu_int, cfg->p_def, priv);
> > + flags, qmenu, qmenu_int, cfg->p_def, cfg->p_min,
> > + cfg->p_max, priv);
> > if (ctrl)
> > ctrl->is_private = cfg->is_private;
> > return ctrl;
> > @@ -1642,7 +1753,8 @@ struct v4l2_ctrl *v4l2_ctrl_new_std(struct v4l2_ctrl_handler *hdl,
> > }
> > return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
> > min, max, step, def, NULL, 0,
> > - flags, NULL, NULL, ptr_null, NULL);
> > + flags, NULL, NULL, ptr_null, ptr_null,
> > + ptr_null, NULL);
> > }
> > EXPORT_SYMBOL(v4l2_ctrl_new_std);
> >
> > @@ -1675,7 +1787,8 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_menu(struct v4l2_ctrl_handler *hdl,
> > }
> > return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
> > 0, max, mask, def, NULL, 0,
> > - flags, qmenu, qmenu_int, ptr_null, NULL);
> > + flags, qmenu, qmenu_int, ptr_null, ptr_null,
> > + ptr_null, NULL);
> > }
> > EXPORT_SYMBOL(v4l2_ctrl_new_std_menu);
> >
> > @@ -1707,7 +1820,8 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_menu_items(struct v4l2_ctrl_handler *hdl,
> > }
> > return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
> > 0, max, mask, def, NULL, 0,
> > - flags, qmenu, NULL, ptr_null, NULL);
> > + flags, qmenu, NULL, ptr_null, ptr_null,
> > + ptr_null, NULL);
> >
> > }
> > EXPORT_SYMBOL(v4l2_ctrl_new_std_menu_items);
> > @@ -1715,7 +1829,9 @@ EXPORT_SYMBOL(v4l2_ctrl_new_std_menu_items);
> > /* Helper function for standard compound controls */
> > struct v4l2_ctrl *v4l2_ctrl_new_std_compound(struct v4l2_ctrl_handler *hdl,
> > const struct v4l2_ctrl_ops *ops, u32 id,
> > - const union v4l2_ctrl_ptr p_def)
> > + const union v4l2_ctrl_ptr p_def,
> > + const union v4l2_ctrl_ptr p_min,
> > + const union v4l2_ctrl_ptr p_max)
> > {
> > const char *name;
> > enum v4l2_ctrl_type type;
> > @@ -1729,7 +1845,7 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_compound(struct v4l2_ctrl_handler *hdl,
> > }
> > return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
> > min, max, step, def, NULL, 0,
> > - flags, NULL, NULL, p_def, NULL);
> > + flags, NULL, NULL, p_def, p_min, p_max, NULL);
> > }
> > EXPORT_SYMBOL(v4l2_ctrl_new_std_compound);
> >
> > @@ -1753,7 +1869,8 @@ struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
> > }
> > return v4l2_ctrl_new(hdl, ops, NULL, id, name, type,
> > 0, max, 0, def, NULL, 0,
> > - flags, NULL, qmenu_int, ptr_null, NULL);
> > + flags, NULL, qmenu_int, ptr_null, ptr_null,
> > + ptr_null, NULL);
> > }
> > EXPORT_SYMBOL(v4l2_ctrl_new_int_menu);
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> > index 21470de62d72..0f713b9a95f9 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -893,7 +893,9 @@ static bool check_ext_ctrls(struct v4l2_ext_controls *c, unsigned long ioctl)
> > return false;
> > break;
> > case V4L2_CTRL_WHICH_DEF_VAL:
> > - /* Default value cannot be changed */
> > + case V4L2_CTRL_WHICH_MIN_VAL:
> > + case V4L2_CTRL_WHICH_MAX_VAL:
> > + /* Default, minimum or maximum value cannot be changed */
> > if (ioctl == VIDIOC_S_EXT_CTRLS ||
> > ioctl == VIDIOC_TRY_EXT_CTRLS) {
> > c->error_idx = c->count;
> > diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> > index 919e104de50b..c8ab8c44d7c6 100644
> > --- a/include/media/v4l2-ctrls.h
> > +++ b/include/media/v4l2-ctrls.h
> > @@ -131,6 +131,8 @@ struct v4l2_ctrl_ops {
> > *
> > * @equal: return true if both values are equal.
> > * @init: initialize the value.
> > + * @minimum: set the value to the minimum value of the control.
> > + * @maximum: set the value to the maximum value of the control.
> > * @log: log the value.
> > * @validate: validate the value. Return 0 on success and a negative value
> > * otherwise.
> > @@ -141,6 +143,10 @@ struct v4l2_ctrl_type_ops {
> > union v4l2_ctrl_ptr ptr2);
> > void (*init)(const struct v4l2_ctrl *ctrl, u32 idx,
> > union v4l2_ctrl_ptr ptr);
> > + void (*minimum)(const struct v4l2_ctrl *ctrl, u32 idx,
> > + union v4l2_ctrl_ptr ptr);
> > + void (*maximum)(const struct v4l2_ctrl *ctrl, u32 idx,
> > + union v4l2_ctrl_ptr ptr);
> > void (*log)(const struct v4l2_ctrl *ctrl);
> > int (*validate)(const struct v4l2_ctrl *ctrl, u32 idx,
> > union v4l2_ctrl_ptr ptr);
> > @@ -237,6 +243,12 @@ typedef void (*v4l2_ctrl_notify_fnc)(struct v4l2_ctrl *ctrl, void *priv);
> > * @p_def: The control's default value represented via a union which
> > * provides a standard way of accessing control types
> > * through a pointer (for compound controls only).
> > + * @p_min: The control's minimum value represented via a union which
> > + * provides a standard way of accessing control types
> > + * through a pointer (for compound controls only).
> > + * @p_max: The control's maximum value represented via a union which
> > + * provides a standard way of accessing control types
> > + * through a pointer (for compound controls only).
> > * @p_cur: The control's current value represented via a union which
> > * provides a standard way of accessing control types
> > * through a pointer.
> > @@ -292,6 +304,8 @@ struct v4l2_ctrl {
> > } cur;
> >
> > union v4l2_ctrl_ptr p_def;
> > + union v4l2_ctrl_ptr p_min;
> > + union v4l2_ctrl_ptr p_max;
> > union v4l2_ctrl_ptr p_new;
> > union v4l2_ctrl_ptr p_cur;
> > };
> > @@ -398,6 +412,8 @@ struct v4l2_ctrl_handler {
> > * @step: The control's step value for non-menu controls.
> > * @def: The control's default value.
> > * @p_def: The control's default value for compound controls.
> > + * @p_min: The control's minimum value for compound controls.
> > + * @p_max: The control's maximum value for compound controls.
> > * @dims: The size of each dimension.
> > * @elem_size: The size in bytes of the control.
> > * @flags: The control's flags.
> > @@ -427,6 +443,8 @@ struct v4l2_ctrl_config {
> > u64 step;
> > s64 def;
> > union v4l2_ctrl_ptr p_def;
> > + union v4l2_ctrl_ptr p_min;
> > + union v4l2_ctrl_ptr p_max;
> > u32 dims[V4L2_CTRL_MAX_DIMS];
> > u32 elem_size;
> > u32 flags;
> > @@ -696,17 +714,21 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_menu_items(struct v4l2_ctrl_handler *hdl,
> > * @ops: The control ops.
> > * @id: The control ID.
> > * @p_def: The control's default value.
> > + * @p_min: The control's minimum value.
> > + * @p_max: The control's maximum value.
> > *
> > - * Sames as v4l2_ctrl_new_std(), but with support to compound controls, thanks
> > - * to the @p_def field. Use v4l2_ctrl_ptr_create() to create @p_def from a
> > - * pointer. Use v4l2_ctrl_ptr_create(NULL) if the default value of the
> > - * compound control should be all zeroes.
> > + * Same as v4l2_ctrl_new_std(), but with support to compound controls, thanks
> > + * to the @p_def/min/max field. Use v4l2_ctrl_ptr_create() to create
>
> s/field/fields/
>
> > + * @p_def/min/max from a pointer. Use v4l2_ctrl_ptr_create(NULL) if the
> > + * default/min/max value of the compound control should be all zeroes.
>
> Hmmm... I expect that, for some compound control types, the concept of
> minimum and maximum won't be defined. Wouldn't it better for a get
> control operation on V4L2_CTRL_WHICH_{MIN,MAX}_VAL to return an error in
> that case, instead of zeroed memory ?
>

Returning error for undefined cases sounds good to me.
What about changing std_min_compound to return error for null ptrs?

+static int std_min_compound(const struct v4l2_ctrl *ctrl, u32 idx,
+ union v4l2_ctrl_ptr ptr)
+{
+ void *p = ptr.p + idx * ctrl->elem_size;
+
+ if (ctrl->p_min.p_const)
+ memcpy(p, ctrl->p_min.p_const, ctrl->elem_size);
+ else
+ return -EINVAL;
+}

Best,
Yunke

>
> > *
> > */
> > struct v4l2_ctrl *v4l2_ctrl_new_std_compound(struct v4l2_ctrl_handler *hdl,
> > const struct v4l2_ctrl_ops *ops,
> > u32 id,
> > - const union v4l2_ctrl_ptr p_def);
> > + const union v4l2_ctrl_ptr p_def,
> > + const union v4l2_ctrl_ptr p_min,
> > + const union v4l2_ctrl_ptr p_max);
> >
> > /**
> > * v4l2_ctrl_new_int_menu() - Create a new standard V4L2 integer menu control.
> > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > index 2e36bb610ea6..134f6a65eacc 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -1796,6 +1796,8 @@ struct v4l2_ext_controls {
> > #define V4L2_CTRL_WHICH_CUR_VAL 0
> > #define V4L2_CTRL_WHICH_DEF_VAL 0x0f000000
> > #define V4L2_CTRL_WHICH_REQUEST_VAL 0x0f010000
> > +#define V4L2_CTRL_WHICH_MIN_VAL 0x0f020000
> > +#define V4L2_CTRL_WHICH_MAX_VAL 0x0f030000
> >
> > enum v4l2_ctrl_type {
> > V4L2_CTRL_TYPE_INTEGER = 1,
>
> --
> Regards,
>
> Laurent Pinchart