7.32. ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY¶

7.32.1. Name¶

VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency

7.32.2. Synopsis¶

int ioctl(int fd, VIDIOC_G_FREQUENCY, struct v4l2_frequency *argp)¶

int ioctl(int fd, VIDIOC_S_FREQUENCY, const struct v4l2_frequency *argp)¶

7.32.3. Arguments¶

fd: File descriptor returned by open().
argp: Pointer to struct v4l2_frequency.

7.32.4. Description¶

To get the current tuner or modulator radio frequency applications set the tuner field of a struct v4l2_frequency to the respective tuner or modulator number (only input devices have tuners, only output devices have modulators), zero out the reserved array and call the VIDIOC_G_FREQUENCY ioctl with a pointer to this structure. The driver stores the current frequency in the frequency field.

To change the current tuner or modulator radio frequency applications initialize the tuner, type and frequency fields, and the reserved array of a struct v4l2_frequency and call the VIDIOC_S_FREQUENCY ioctl with a pointer to this structure. When the requested frequency is not possible the driver assumes the closest possible value. However VIDIOC_S_FREQUENCY is a write-only ioctl, it does not return the actual new frequency.

v4l2_frequency¶

struct v4l2_frequency¶
__u32	`tuner`	The tuner or modulator index number. This is the same value as in the struct `v4l2_input` `tuner` field and the struct `v4l2_tuner` `index` field, or the struct `v4l2_output` `modulator` field and the struct `v4l2_modulator` `index` field.
__u32	`type`	The tuner type. This is the same value as in the struct `v4l2_tuner` `type` field. The type must be set to `V4L2_TUNER_RADIO` for `/dev/radioX` device nodes, and to `V4L2_TUNER_ANALOG_TV` for all others. Set this field to `V4L2_TUNER_RADIO` for modulators (currently only radio modulators are supported). See `v4l2_tuner_type`
__u32	`frequency`	Tuning frequency in units of 62.5 kHz, or if the struct `v4l2_tuner` or struct `v4l2_modulator` `capability` flag `V4L2_TUNER_CAP_LOW` is set, in units of 62.5 Hz. A 1 Hz unit is used when the `capability` flag `V4L2_TUNER_CAP_1HZ` is set.
__u32	`reserved`[8]	Reserved for future extensions. Drivers and applications must set the array to zero.

7.32.5. Return Value¶

On success 0 is returned, on error -1 and the errno variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.

EINVAL: The tuner index is out of bounds or the value in the type field is wrong.
EBUSY: A hardware seek is in progress.