VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY — Get or set tuner or modulator radio frequency


int ioctl(int fd,
 int request,
 struct v4l2_frequency *argp);
int ioctl(int fd,
 int request,
 const struct v4l2_frequency *argp);



File descriptor returned by open().





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.

Table A.73. struct v4l2_frequency

__u32tunerThe 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.
__u32typeThe 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 Table A.88, “enum v4l2_tuner_type”
__u32frequencyTuning 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.
__u32reserved[8]Reserved for future extensions. Drivers and applications must set the array to zero.

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.


The tuner index is out of bounds or the value in the type field is wrong.


A hardware seek is in progress.