V4L/DVB (3245): Added some comments about multiple tuner support.
- Added some comments to make clearer how to use ioctl api to handle
multiple tuners at the same board.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>
diff --git a/include/media/tuner.h b/include/media/tuner.h
index aa91ce3..c5f034e 100644
--- a/include/media/tuner.h
+++ b/include/media/tuner.h
@@ -150,10 +150,26 @@
T_STANDBY = 1 << 31
};
+/* Older boards only had a single tuner device. Nowadays multiple tuner
+ devices may be present on a single board. Using TUNER_SET_TYPE_ADDR
+ to pass the tuner_setup structure it is possible to setup each tuner
+ device in turn.
+
+ Since multiple devices may be present it is no longer sufficient to
+ send a command to a single i2c device. Instead you should broadcast
+ the command to all i2c devices.
+
+ By setting the mode_mask correctly you can select which commands are
+ accepted by a specific tuner device. For example, set mode_mask to
+ T_RADIO if the device is a radio-only tuner. That specific tuner will
+ only accept commands when the tuner is in radio mode and ignore them
+ when the tuner is set to TV mode.
+ */
+
struct tuner_setup {
- unsigned short addr;
- unsigned int type;
- unsigned int mode_mask;
+ unsigned short addr; /* I2C address */
+ unsigned int type; /* Tuner type */
+ unsigned int mode_mask; /* Allowed tuner modes */
};
struct tuner {