7.5. ioctl VIDIOC_DBG_G_CHIP_INFO¶
VIDIOC_DBG_G_CHIP_INFO - Identify the chips on a TV card
int ioctl(int fd, VIDIOC_DBG_G_CHIP_INFO, struct v4l2_dbg_chip_info *argp)
- File descriptor returned by
- Pointer to struct
This is an Experimental API Elements interface and may change in the future.
For driver debugging purposes this ioctl allows test applications to query the driver about the chips present on the TV card. Regular applications must not use it. When you found a chip specific bug, please contact the linux-media mailing list (https://linuxtv.org/lists.php) so it can be fixed.
Additionally the Linux kernel must be compiled with the
CONFIG_VIDEO_ADV_DEBUG option to enable this ioctl.
To query the driver applications must initialize the
match.name fields of a struct
v4l2_dbg_chip_info and call
ioctl VIDIOC_DBG_G_CHIP_INFO with a pointer to this structure. On success
the driver stores information about the selected chip in the
selects the nth bridge ‘chip’ on the TV card. You can enumerate all
chips by starting at zero and incrementing
match.addr by one until
ioctl VIDIOC_DBG_G_CHIP_INFO fails with an
EINVAL error code. The number
zero always selects the bridge chip itself, e. g. the chip connected to
the PCI or USB bus. Non-zero numbers identify specific parts of the
bridge chip such as an AC97 register block.
selects the nth sub-device. This allows you to enumerate over all
On success, the
name field will contain a chip name and the
flags field will contain
V4L2_CHIP_FL_READABLE if the driver
supports reading registers from the device or
if the driver supports writing registers to the device.
We recommended the v4l2-dbg utility over calling this ioctl directly. It is available from the LinuxTV v4l-dvb repository; see https://linuxtv.org/repo/ for access instructions.
||See Chip Match Types for a list of possible types.|
||Match a chip by this number, interpreted according to the
||Match a chip by this name, interpreted according to the
||How to match the chip, see struct v4l2_dbg_match.|
||The name of the chip.|
||Set by the driver. If
||Reserved fields, both application and driver must set these to 0.|
||0||Match the nth chip on the card, zero for the bridge chip. Does not match sub-devices.|
||4||Match the nth sub-device.|
7.5.5. 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.
match_typeis invalid or no device could be matched.