VIDIOC_DBG_G_CHIP_INFO — Identify the chips on a TV card
int ioctl( | int fd, |
| int request, | |
struct v4l2_dbg_chip_info
*argp); |
This is an experimental 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 (http://www.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.type and
match.addr or match.name
fields of a struct v4l2_dbg_chip_info
and call VIDIOC_DBG_G_CHIP_INFO with a pointer to
this structure. On success the driver stores information about the
selected chip in the name and
flags fields.
When match.type is
V4L2_CHIP_MATCH_BRIDGE,
match.addr 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
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.
When match.type is
V4L2_CHIP_MATCH_SUBDEV,
match.addr selects the nth sub-device. This
allows you to enumerate over all sub-devices.
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 V4L2_CHIP_FL_WRITABLE
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 http://linuxtv.org/repo/ for access instructions.
Table A.4. struct v4l2_dbg_match
| __u32 | type | See Table A.6, “Chip Match Types” for a list of possible types. | |
| union | (anonymous) | ||
| __u32 | addr | Match a chip by this number, interpreted according
to the type field. | |
| char | name[32] | Match a chip by this name, interpreted according
to the type field. Currently unused. |
Table A.5. struct v4l2_dbg_chip_info
| struct v4l2_dbg_match | match | How to match the chip, see Table A.4, “struct v4l2_dbg_match”. |
| char | name[32] | The name of the chip. |
| __u32 | flags | Set by the driver. If V4L2_CHIP_FL_READABLE
is set, then the driver supports reading registers from the device. If
V4L2_CHIP_FL_WRITABLE is set, then it supports writing registers. |
| __u32 | reserved[8] | Reserved fields, both application and driver must set these to 0. |
Table A.6. Chip Match Types
V4L2_CHIP_MATCH_BRIDGE | 0 | Match the nth chip on the card, zero for the bridge chip. Does not match sub-devices. |
V4L2_CHIP_MATCH_SUBDEV | 4 | Match the nth sub-device. |
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 match_type is invalid or
no device could be matched.