From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- .../DocBook/v4l/vidioc-dbg-g-register.xml | 275 +++++++++++++++++++++ 1 file changed, 275 insertions(+) create mode 100644 Documentation/DocBook/v4l/vidioc-dbg-g-register.xml (limited to 'Documentation/DocBook/v4l/vidioc-dbg-g-register.xml') diff --git a/Documentation/DocBook/v4l/vidioc-dbg-g-register.xml b/Documentation/DocBook/v4l/vidioc-dbg-g-register.xml new file mode 100644 index 00000000..980c7f3e --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-dbg-g-register.xml @@ -0,0 +1,275 @@ + + + ioctl VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER + &manvol; + + + + VIDIOC_DBG_G_REGISTER + VIDIOC_DBG_S_REGISTER + Read or write hardware registers + + + + + + int ioctl + int fd + int request + struct v4l2_dbg_register *argp + + + + + int ioctl + int fd + int request + const struct v4l2_dbg_register +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER + + + + argp + + + + + + + + + Description + + + Experimental + + This is an experimental +interface and may change in the future. + + + For driver debugging purposes these ioctls allow test +applications to access hardware registers directly. Regular +applications must not use them. + + Since writing or even reading registers can jeopardize the +system security, its stability and damage the hardware, both ioctls +require superuser privileges. Additionally the Linux kernel must be +compiled with the CONFIG_VIDEO_ADV_DEBUG option +to enable these ioctls. + + To write a register applications must initialize all fields +of a &v4l2-dbg-register; and call +VIDIOC_DBG_S_REGISTER with a pointer to this +structure. The match.type and +match.addr or match.name +fields select a chip on the TV +card, the reg field specifies a register +number and the val field the value to be +written into the register. + + To read a register applications must initialize the +match.type, +match.chip or match.name and +reg fields, and call +VIDIOC_DBG_G_REGISTER with a pointer to this +structure. On success the driver stores the register value in the +val field. 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. The number zero always selects the host chip, ⪚ the +chip connected to the PCI or USB bus. You can find out which chips are +present with the &VIDIOC-DBG-G-CHIP-IDENT; ioctl. + + 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 +effect of these ioctls is undefined. Again with the +&VIDIOC-DBG-G-CHIP-IDENT; ioctl you can find out which &i2c; chips are +present. + + 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. + + + Success not guaranteed + + Due to a flaw in the Linux &i2c; bus driver these ioctls may +return successfully without actually reading or writing a register. To +catch the most likely failure we recommend a &VIDIOC-DBG-G-CHIP-IDENT; +call confirming the presence of the selected &i2c; chip. + + + These ioctls are optional, not all drivers may support them. +However when a driver supports these ioctls it must also support +&VIDIOC-DBG-G-CHIP-IDENT;. Conversely it may support +VIDIOC_DBG_G_CHIP_IDENT but not these ioctls. + + VIDIOC_DBG_G_REGISTER and +VIDIOC_DBG_S_REGISTER were introduced in Linux +2.6.21, but their API was changed to the one described here in kernel 2.6.29. + + We recommended the v4l2-dbg +utility over calling these ioctls directly. It is available from the +LinuxTV v4l-dvb repository; see http://linuxtv.org/repo/ for +access instructions. + + + + struct <structname>v4l2_dbg_match</structname> + + &cs-ustr; + + + __u32 + type + See 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. + + + +
+ + + + struct <structname>v4l2_dbg_register</structname> + + + + + + + struct v4l2_dbg_match + match + How to match the chip, see . + + + __u64 + reg + A register number. + + + __u64 + val + The value read from, or to be written into the +register. + + + +
+ + + + Chip Match Types + + &cs-def; + + + 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. + + + +
+ + + + &return-value; + + + + EINVAL + + The driver does not support this ioctl, or the kernel +was not compiled with the CONFIG_VIDEO_ADV_DEBUG +option, or the match_type is invalid, or the +selected chip or register does not exist. + + + + EPERM + + Insufficient permissions. Root privileges are required +to execute these ioctls. + + + + + + + -- cgit v1.2.3