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Message-ID: <20250818155809.469479-4-mirela.rabulea@nxp.com>
Date: Mon, 18 Aug 2025 18:58:07 +0300
From: Mirela Rabulea <mirela.rabulea@....com>
To: mchehab@...nel.org,
sakari.ailus@...ux.intel.com,
hverkuil-cisco@...all.nl,
laurent.pinchart+renesas@...asonboard.com,
ribalda@...omium.org,
jai.luthra@...asonboard.com,
laurentiu.palcu@....com
Cc: linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org,
LnxRevLi@....com,
julien.vuillaumier@....com,
celine.laurencin@....com
Subject: [RFC v2 3/5] media: v4l2-ctrls: Add v4l2 helper functions for single-capture controls
Add v4l2 helper functions to support backward compatibility
with older user-space applications that are still using the
single-capture exposure and gain controls.
After the addition of multi-capture exposure and gain controls,
the following scenarios are possible:
1. Old applications & old sensor drivers
Both the application and the driver are using single-capture controls,
no problem here.
2. Old applications & new sensor drivers
The application is using single-capture controls and we want the drivers
to implement only the new multi-capture controls. In this case the
driver should use the v4l2_ctrl_new_single_cap_ctrls helper to create
the old single-capture controls, for backward compatibility.
3. New application & old sensor drivers
The new application can query if the driver supports multi-capture
controls, if it doesn't, the application may fallback to single-capture
controls.
4. New application & new sensor drivers
Both the application and the driver are using multi-capture controls,
again, no problem here.
Signed-off-by: Mirela Rabulea <mirela.rabulea@....com>
---
Changes in v2:
New patch
drivers/media/v4l2-core/v4l2-ctrls-core.c | 85 +++++++++++++++++++++++
include/media/v4l2-ctrls.h | 76 ++++++++++++++++++++
2 files changed, 161 insertions(+)
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
index 98b960775e87..41f307e3afa6 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
@@ -2719,3 +2719,88 @@ int v4l2_ctrl_new_fwnode_properties(struct v4l2_ctrl_handler *hdl,
return hdl->error;
}
EXPORT_SYMBOL(v4l2_ctrl_new_fwnode_properties);
+
+int v4l2_ctrl_new_single_cap_ctrls(struct v4l2_ctrl_handler *hdl,
+ const struct v4l2_ctrl_ops *ctrl_ops)
+{
+ if (hdl->error)
+ return hdl->error;
+
+ v4l2_ctrl_new_std(hdl, ctrl_ops, V4L2_CID_EXPOSURE,
+ 0, 0, 1, 0);
+
+ v4l2_ctrl_new_std(hdl, ctrl_ops, V4L2_CID_ANALOGUE_GAIN,
+ 0, 0, 1, 0);
+
+ v4l2_ctrl_new_std(hdl, ctrl_ops, V4L2_CID_DIGITAL_GAIN,
+ 0, 0, 1, 0);
+
+ return hdl->error;
+}
+EXPORT_SYMBOL(v4l2_ctrl_new_single_cap_ctrls);
+
+struct v4l2_ctrl *__v4l2_get_multi_ctrl(struct v4l2_ctrl *ctrl_single)
+{
+ struct v4l2_ctrl_handler *hdl = ctrl_single->handler;
+ struct v4l2_ctrl_ref *ref;
+
+ switch (ctrl_single->id) {
+ case V4L2_CID_EXPOSURE:
+ ref = find_ref(hdl, V4L2_CID_EXPOSURE_MULTI);
+ break;
+ case V4L2_CID_ANALOGUE_GAIN:
+ ref = find_ref(hdl, V4L2_CID_AGAIN_MULTI);
+ break;
+ case V4L2_CID_DIGITAL_GAIN:
+ ref = find_ref(hdl, V4L2_CID_DGAIN_MULTI);
+ break;
+ default:
+ return NULL;
+ }
+
+ return ref->ctrl;
+}
+EXPORT_SYMBOL(__v4l2_get_multi_ctrl);
+
+struct v4l2_ctrl *__v4l2_get_single_ctrl(struct v4l2_ctrl *ctrl_multi)
+{
+ struct v4l2_ctrl_handler *hdl = ctrl_multi->handler;
+ struct v4l2_ctrl_ref *ref;
+
+ switch (ctrl_multi->id) {
+ case V4L2_CID_EXPOSURE_MULTI:
+ ref = find_ref(hdl, V4L2_CID_EXPOSURE);
+ break;
+ case V4L2_CID_AGAIN_MULTI:
+ ref = find_ref(hdl, V4L2_CID_ANALOGUE_GAIN);
+ break;
+ case V4L2_CID_DGAIN_MULTI:
+ ref = find_ref(hdl, V4L2_CID_DIGITAL_GAIN);
+ break;
+ default:
+ return NULL;
+ }
+
+ return ref->ctrl;
+}
+EXPORT_SYMBOL(__v4l2_get_single_ctrl);
+
+int __v4l2_s_ctrl_multi_to_single(struct v4l2_ctrl *ctrl_multi)
+{
+ struct v4l2_ctrl *ctrl_single = NULL;
+
+ if (!ctrl_multi)
+ return -EINVAL;
+
+ ctrl_single = __v4l2_get_single_ctrl(ctrl_multi);
+ /* don't fail if no corresponding single control is found */
+ if (!ctrl_single)
+ return 0;
+
+ /* update the value of the single control, without calling s_ctrl */
+ ctrl_single->cur.val = ctrl_multi->p_cur.p_u32[0];
+
+ return 0;
+}
+EXPORT_SYMBOL(__v4l2_s_ctrl_multi_to_single);
+
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index 4a294a5c7bdd..d3a9dde47349 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -1587,6 +1587,82 @@ int v4l2_ctrl_new_fwnode_properties(struct v4l2_ctrl_handler *hdl,
const struct v4l2_ctrl_ops *ctrl_ops,
const struct v4l2_fwnode_device_properties *p);
+/**
+ * v4l2_ctrl_new_single_cap_ctrls() - Register single capture controls for
+ * backward compatibility
+ *
+ * @hdl: pointer to &struct v4l2_ctrl_handler to register controls on
+ * @ctrl_ops: pointer to &struct v4l2_ctrl_ops to register controls with
+ *
+ * This function registers the single capture controls for exposure
+ * and gains, for backward compatibility with userspace applications that
+ * do not use yet the new, multi-capture controls.
+ *
+ * Currently, the following v4l2 controls are parsed and registered:
+ * - V4L2_CID_EXPOSURE
+ * - V4L2_CID_ANALOGUE_GAIN
+ * - V4L2_CID_DIGITAL_GAIN;
+ *
+ * Controls already registered by the caller with the @hdl control handler are
+ * not overwritten. Callers should register the controls they want to handle
+ * themselves before calling this function.
+ *
+ * Return: 0 on success, a negative error code on failure.
+ */
+int v4l2_ctrl_new_single_cap_ctrls(struct v4l2_ctrl_handler *hdl,
+ const struct v4l2_ctrl_ops *ctrl_ops);
+
+/**
+ * __v4l2_get_multi_ctrl() - Return the multi-capture controls for a given
+ * single-capture control
+ *
+ * @ctrl_single: pointer to &struct v4l2_ctrl for the single-capture control
+ *
+ * This function finds the corresponding multi-capture control for a given
+ * single-capture control.
+ *
+ * This function assumes the control's handler is already locked,
+ * allowing it to be used from within the &v4l2_ctrl_ops functions.
+ *
+ * Return: a pointer to the multi-capture control if found, NULL otherwise.
+ */
+struct v4l2_ctrl *__v4l2_get_multi_ctrl(struct v4l2_ctrl *ctrl_single);
+
+/**
+ * __v4l2_get_single_ctrl() - Return the single-capture controls for a given
+ * multi-capture control
+ *
+ * @ctrl_multi: pointer to &struct v4l2_ctrl for the multi-capture control
+ *
+ * This function finds the corresponding single-capture control for a given
+ * multi-capture control.
+ *
+ * This function assumes the control's handler is already locked,
+ * allowing it to be used from within the &v4l2_ctrl_ops functions.
+ *
+ * Return: a pointer to the single-capture control if found, NULL otherwise.
+ */
+struct v4l2_ctrl *__v4l2_get_single_ctrl(struct v4l2_ctrl *ctrl_multi);
+
+/**
+ * __v4l2_s_ctrl_multi_to_single() - Set the single-capture control for a
+ * given multi-capture control
+ *
+ * @ctrl_multi: pointer to &struct v4l2_ctrl for the multi-capture control
+ *
+ * This function finds the corresponding single-capture control for a given
+ * multi-capture control, and updates single-capture control with the value
+ * from the first element of the multie-capture control, to ensure
+ * backward compatibility with older user-space applications that still use
+ * the single-capture exposure and gain controls.
+ *
+ * This function assumes the control's handler is already locked,
+ * allowing it to be used from within the &v4l2_ctrl_ops functions.
+ *
+ * Return: 0 on success, a negative error code on failure.
+ */
+int __v4l2_s_ctrl_multi_to_single(struct v4l2_ctrl *ctrl_multi);
+
/**
* v4l2_ctrl_type_op_equal - Default v4l2_ctrl_type_ops equal callback.
*
--
2.43.0
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