Name

VIDIOC_DBG_G_CHIP_IDENT — Identify the chips on a TV card

Synopsis

int ioctl(int fd,
 int request,
 struct v4l2_dbg_chip_ident *argp);
 

Arguments

fd

File descriptor returned by open().

request

VIDIOC_DBG_G_CHIP_IDENT

argp

Description

Experimental

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.

To query the driver applications must initialize the match.type and match.addr or match.name fields of a struct v4l2_dbg_chip_ident and call VIDIOC_DBG_G_CHIP_IDENT with a pointer to this structure. On success the driver stores information about the selected chip in the ident and revision fields. On failure the structure remains unchanged.

When match.type is V4L2_CHIP_MATCH_HOST, match.addr selects the nth non-I2C 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_IDENT fails with an EINVAL error code. The number zero always selects the host chip, e. g. the chip connected to the PCI or USB bus.

When match.type is V4L2_CHIP_MATCH_I2C_DRIVER, match.name contains the I2C driver name. For instance "saa7127" will match any chip supported by the saa7127 driver, regardless of its I2C bus address. When multiple chips supported by the same driver are present, the ioctl will return V4L2_IDENT_AMBIGUOUS in the ident field.

When match.type is V4L2_CHIP_MATCH_I2C_ADDR, match.addr selects a chip by its 7 bit I2C bus address.

When match.type is V4L2_CHIP_MATCH_AC97, match.addr selects the nth AC97 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_IDENT fails with an EINVAL error code.

On success, the ident field will contain a chip ID from the Linux media/v4l2-chip-ident.h header file, and the revision field will contain a driver specific value, or zero if no particular revision is associated with this chip.

When the driver could not identify the selected chip, ident will contain V4L2_IDENT_UNKNOWN. When no chip matched the ioctl will succeed but the ident field will contain V4L2_IDENT_NONE. If multiple chips matched, ident will contain V4L2_IDENT_AMBIGUOUS. In all these cases the revision field remains unchanged.

This ioctl is optional, not all drivers may support it. It was introduced in Linux 2.6.21, but the API was changed to the one described here in 2.6.29.

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

__u32typeSee Table A.6, “Chip Match Types” for a list of possible types. 
union(anonymous)  
 __u32addrMatch a chip by this number, interpreted according to the type field.
 charname[32]Match a chip by this name, interpreted according to the type field.

Table A.5. struct v4l2_dbg_chip_ident

struct v4l2_dbg_matchmatchHow to match the chip, see Table A.4, “struct v4l2_dbg_match.
__u32identA chip identifier as defined in the Linux media/v4l2-chip-ident.h header file, or one of the values from Table A.7, “Chip Identifiers”.
__u32revisionA chip revision, chip and driver specific.

Table A.6. Chip Match Types

V4L2_CHIP_MATCH_HOST0Match the nth chip on the card, zero for the host chip. Does not match I2C chips.
V4L2_CHIP_MATCH_I2C_DRIVER1Match an I2C chip by its driver name.
V4L2_CHIP_MATCH_I2C_ADDR2Match a chip by its 7 bit I2C bus address.
V4L2_CHIP_MATCH_AC973Match the nth anciliary AC97 chip.

Table A.7. Chip Identifiers

V4L2_IDENT_NONE0No chip matched.
V4L2_IDENT_AMBIGUOUS1Multiple chips matched.
V4L2_IDENT_UNKNOWN2A chip is present at this address, but the driver could not identify it.

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 match_type is invalid.