VIDIOC_S_HW_FREQ_SEEK — Perform a hardware frequency seek
int ioctl( | int fd, |
| int request, | |
struct v4l2_hw_freq_seek
*argp); |
Start a hardware frequency seek from the current frequency.
To do this applications initialize the tuner,
type, seek_upward,
wrap_around, spacing,
rangelow and rangehigh
fields, and zero out the reserved array of a
struct v4l2_hw_freq_seek and call the VIDIOC_S_HW_FREQ_SEEK
ioctl with a pointer to this structure.
The rangelow and
rangehigh fields can be set to a non-zero value to
tell the driver to search a specific band. If the struct v4l2_tuner
capability field has the
V4L2_TUNER_CAP_HWSEEK_PROG_LIM flag set, these values
must fall within one of the bands returned by VIDIOC_ENUM_FREQ_BANDS. If
the V4L2_TUNER_CAP_HWSEEK_PROG_LIM flag is not set,
then these values must exactly match those of one of the bands returned by
VIDIOC_ENUM_FREQ_BANDS. If the current frequency of the tuner does not fall
within the selected band it will be clamped to fit in the band before the
seek is started.
If an error is returned, then the original frequency will be restored.
This ioctl is supported if the V4L2_CAP_HW_FREQ_SEEK capability is set.
If this ioctl is called from a non-blocking filehandle, then EAGAIN error code is returned and no seek takes place.
Table A.101. struct v4l2_hw_freq_seek
| __u32 | tuner | The tuner index number. This is the
same value as in the struct v4l2_input tuner
field and the struct v4l2_tuner index field. |
| __u32 | type | The tuner type. This is the same value as in the
struct v4l2_tuner type field. See Table A.88, “enum v4l2_tuner_type” |
| __u32 | seek_upward | If non-zero, seek upward from the current frequency, else seek downward. |
| __u32 | wrap_around | If non-zero, wrap around when at the end of the frequency range, else stop seeking.
The struct v4l2_tuner capability field will tell you what the
hardware supports.
|
| __u32 | spacing | If non-zero, defines the hardware seek resolution in Hz. The driver selects the nearest value that is supported by the device. If spacing is zero a reasonable default value is used. |
| __u32 | rangelow | If non-zero, the lowest tunable frequency of the band to
search in units of 62.5 kHz, or if the struct v4l2_tuner
capability field has the
V4L2_TUNER_CAP_LOW flag set, in units of 62.5 Hz or if the struct v4l2_tuner
capability field has the
V4L2_TUNER_CAP_1HZ flag set, in units of 1 Hz.
If rangelow is zero a reasonable default value
is used. |
| __u32 | rangehigh | If non-zero, the highest tunable frequency of the band to
search in units of 62.5 kHz, or if the struct v4l2_tuner
capability field has the
V4L2_TUNER_CAP_LOW flag set, in units of 62.5 Hz or if the struct v4l2_tuner
capability field has the
V4L2_TUNER_CAP_1HZ flag set, in units of 1 Hz.
If rangehigh is zero a reasonable default value
is used. |
| __u32 | reserved[5] | Reserved for future extensions. Applications must set the array to zero. |
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, the wrap_around value is not supported or
one of the values in the type,
rangelow or rangehigh
fields is wrong.
Attempted to call VIDIOC_S_HW_FREQ_SEEK
with the filehandle in non-blocking mode.
The hardware seek found no channels.
Another hardware seek is already in progress.