VIDIOC_DBG_G_CHIP_IDENT — Identify the chips on a TV card
int ioctl( | int | fd, |
| int | request, | |
| struct v4l2_dbg_chip_ident * | 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 (https://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 https://linuxtv.org/repo/ for access instructions.
Table 41. struct v4l2_dbg_match
| __u32 | type | See Table 43, “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. |
Table 42. struct v4l2_dbg_chip_ident
| struct v4l2_dbg_match | match | How to match the chip, see Table 41, “struct v4l2_dbg_match”. |
| __u32 | ident | A chip identifier as defined in the Linux
media/v4l2-chip-ident.h header file, or one of
the values from Table 44, “Chip Identifiers”. |
| __u32 | revision | A chip revision, chip and driver specific. |
Table 43. Chip Match Types
V4L2_CHIP_MATCH_HOST | 0 | Match the nth chip on the card, zero for the host chip. Does not match I2C chips. |
V4L2_CHIP_MATCH_I2C_DRIVER | 1 | Match an I2C chip by its driver name. |
V4L2_CHIP_MATCH_I2C_ADDR | 2 | Match a chip by its 7 bit I2C bus address. |
V4L2_CHIP_MATCH_AC97 | 3 | Match the nth anciliary AC97 chip. |
Table 44. Chip Identifiers
V4L2_IDENT_NONE | 0 | No chip matched. |
V4L2_IDENT_AMBIGUOUS | 1 | Multiple chips matched. |
V4L2_IDENT_UNKNOWN | 2 | A chip is present at this address, but the driver could not identify it. |