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-rw-r--r--include/media/v4l2-subdev.h21
1 files changed, 20 insertions, 1 deletions
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 5459bcf5a423..a6a9e54388e2 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -215,7 +215,10 @@ struct v4l2_subdev_core_ops {
* struct v4l2_subdev_tuner_ops - Callbacks used when v4l device was opened
* in radio mode.
*
- * @s_radio: callback for VIDIOC_S_RADIO() ioctl handler code.
+ * @s_radio: callback that switches the tuner to radio mode.
+ * drivers should explicitly call it when a tuner ops should
+ * operate on radio mode, before being able to handle it.
+ * Used on devices that have both AM/FM radio receiver and TV.
*
* @s_frequency: callback for VIDIOC_S_FREQUENCY() ioctl handler code.
*
@@ -238,6 +241,22 @@ struct v4l2_subdev_core_ops {
* @s_type_addr: sets tuner type and its I2C addr.
*
* @s_config: sets tda9887 specific stuff, like port1, port2 and qss
+ *
+ * .. note::
+ *
+ * On devices that have both AM/FM and TV, it is up to the driver
+ * to explicitly call s_radio when the tuner should be switched to
+ * radio mode, before handling other &struct v4l2_subdev_tuner_ops
+ * that would require it. An example of such usage is::
+ *
+ * static void s_frequency(void *priv, const struct v4l2_frequency *f)
+ * {
+ * ...
+ * if (f.type == V4L2_TUNER_RADIO)
+ * v4l2_device_call_all(v4l2_dev, 0, tuner, s_radio);
+ * ...
+ * v4l2_device_call_all(v4l2_dev, 0, tuner, s_frequency);
+ * }
*/
struct v4l2_subdev_tuner_ops {
int (*s_radio)(struct v4l2_subdev *sd);

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