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>
This commit is contained in:
Hans Verkuil 2006-01-09 15:25:39 -02:00 committed by Mauro Carvalho Chehab
parent 66e33dee9e
commit a544521ef0

View File

@ -150,10 +150,26 @@ enum tuner_mode {
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 {