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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| ><TR |
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| ><H1 |
| ><A |
| NAME="VIDIOC-DBG-G-REGISTER" |
| ></A |
| >ioctl VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN7904" |
| ></A |
| ><H2 |
| >Name</H2 |
| >VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER -- Read or write hardware registers</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN7908" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN7909" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, struct v4l2_register *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN7919" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, const struct v4l2_register |
| *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7929" |
| ></A |
| ><H2 |
| >Arguments</H2 |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| ></DT |
| ><DD |
| ><P |
| >File descriptor returned by <A |
| HREF="r14090.htm" |
| ><CODE |
| CLASS="FUNCTION" |
| >open()</CODE |
| ></A |
| >.</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >request</CODE |
| ></DT |
| ><DD |
| ><P |
| >VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| ></DT |
| ><DD |
| ><P |
| ></P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7949" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><DIV |
| CLASS="NOTE" |
| ><BLOCKQUOTE |
| CLASS="NOTE" |
| ><P |
| ><B |
| >Experimental: </B |
| >This is an <A |
| HREF="x16453.htm" |
| >experimental</A |
| > |
| interface and may change in the future.</P |
| ></BLOCKQUOTE |
| ></DIV |
| ><P |
| >For driver debugging purposes these ioctls allow test |
| applications to access hardware registers directly. Regular |
| applications should not use them.</P |
| ><P |
| >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 <CODE |
| CLASS="CONSTANT" |
| >CONFIG_VIDEO_ADV_DEBUG</CODE |
| > option |
| to enable these ioctls.</P |
| ><P |
| >To write a register applications must initialize all fields |
| of a struct <A |
| HREF="r7900.htm#V4L2-REGISTER" |
| >v4l2_register</A |
| > and call |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_DBG_S_REGISTER</CODE |
| > with a pointer to this |
| structure. The <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| > and |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| > fields select a chip on the TV |
| card, the <CODE |
| CLASS="STRUCTFIELD" |
| >reg</CODE |
| > field specifies a register |
| number and the <CODE |
| CLASS="STRUCTFIELD" |
| >val</CODE |
| > field the value to be |
| written into the register.</P |
| ><P |
| >To read a register applications must initialize the |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| >, |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| > and |
| <CODE |
| CLASS="STRUCTFIELD" |
| >reg</CODE |
| > fields, and call |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_DBG_G_REGISTER</CODE |
| > with a pointer to this |
| structure. On success the driver stores the register value in the |
| <CODE |
| CLASS="STRUCTFIELD" |
| >val</CODE |
| > field. On failure the structure remains |
| unchanged.</P |
| ><P |
| >When <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| > is |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_CHIP_MATCH_HOST</CODE |
| >, |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| > selects the nth non-I<SUP |
| >2</SUP |
| >C chip |
| on the TV card. Drivers may also interpret |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| > as a random ID, but we recommend |
| against that. The number zero always selects the host chip, e. g. the |
| chip connected to the PCI bus. You can find out which chips are |
| present with the <A |
| HREF="r9804.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CHIP_IDENT</CODE |
| ></A |
| > ioctl.</P |
| ><P |
| >When <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| > is |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_CHIP_MATCH_I2C_DRIVER</CODE |
| >, |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| > contains a driver ID as defined |
| in the <TT |
| CLASS="FILENAME" |
| >linux/i2c-id.h</TT |
| > header file. For instance |
| <CODE |
| CLASS="CONSTANT" |
| >I2C_DRIVERID_SAA7127</CODE |
| > will match any chip |
| supported by the saa7127 driver, regardless of its I<SUP |
| >2</SUP |
| >C bus address. |
| When multiple chips supported by the same driver are present, the |
| effect of these ioctls is undefined. Again with the |
| <A |
| HREF="r9804.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CHIP_IDENT</CODE |
| ></A |
| > ioctl you can find out which I<SUP |
| >2</SUP |
| >C chips are |
| present.</P |
| ><P |
| >When <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| > is |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_CHIP_MATCH_I2C_ADDR</CODE |
| >, |
| <CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| > selects a chip by its 7 bit I<SUP |
| >2</SUP |
| >C |
| bus address.</P |
| ><DIV |
| CLASS="NOTE" |
| ><BLOCKQUOTE |
| CLASS="NOTE" |
| ><P |
| ><B |
| >Success not guaranteed: </B |
| >Due to a flaw in the Linux I<SUP |
| >2</SUP |
| >C bus driver these ioctls may |
| return successfully without actually reading or writing a register. To |
| catch the most likely failure we recommend a <A |
| HREF="r9804.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CHIP_IDENT</CODE |
| ></A |
| > |
| call confirming the presence of the selected I<SUP |
| >2</SUP |
| >C chip.</P |
| ></BLOCKQUOTE |
| ></DIV |
| ><P |
| >These ioctls are optional, not all drivers may support them. |
| However when a driver supports these ioctls it must also support |
| <A |
| HREF="r9804.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CHIP_IDENT</CODE |
| ></A |
| >. Conversely it may support |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CHIP_IDENT</CODE |
| > but not these ioctls.</P |
| ><P |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_DBG_G_REGISTER</CODE |
| > and |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_DBG_S_REGISTER</CODE |
| > were introduced in Linux |
| 2.6.21.</P |
| ><P |
| >We recommended the <SPAN |
| CLASS="APPLICATION" |
| >v4l2-dbg</SPAN |
| > |
| utility over calling these ioctls directly. It is available from the |
| LinuxTV v4l-dvb repository; see <A |
| HREF="http://linuxtv.org/repo/" |
| TARGET="_top" |
| >http://linuxtv.org/repo/</A |
| > for |
| access instructions.</P |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-REGISTER" |
| ></A |
| ><P |
| ><B |
| >Table 1. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_register</CODE |
| ></B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
| WIDTH="100%" |
| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="33%" |
| TITLE="C1"><COL |
| WIDTH="33%" |
| TITLE="C2"><COL |
| WIDTH="33%" |
| TITLE="C4"><COL><TBODY |
| VALIGN="TOP" |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| ></TD |
| ><TD |
| >See <A |
| HREF="r7900.htm#CHIP-MATCH-TYPES" |
| >Table 2</A |
| > for a list of |
| possible types.</TD |
| ><TD |
| > </TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >match_chip</CODE |
| ></TD |
| ><TD |
| >Match a chip by this number, interpreted according |
| to the <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| > field.</TD |
| ><TD |
| > </TD |
| ></TR |
| ><TR |
| ><TD |
| >__u64</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >reg</CODE |
| ></TD |
| ><TD |
| >A register number.</TD |
| ><TD |
| > </TD |
| ></TR |
| ><TR |
| ><TD |
| >__u64</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >val</CODE |
| ></TD |
| ><TD |
| >The value read from, or to be written into the |
| register.</TD |
| ><TD |
| > </TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="CHIP-MATCH-TYPES" |
| ></A |
| ><P |
| ><B |
| >Table 2. Chip Match Types</B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
| WIDTH="100%" |
| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="38%" |
| TITLE="C1"><COL |
| WIDTH="12%" |
| TITLE="C2"><COL |
| WIDTH="50%" |
| TITLE="C3"><TBODY |
| VALIGN="TOP" |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CHIP_MATCH_HOST</CODE |
| ></TD |
| ><TD |
| >0</TD |
| ><TD |
| >Match the nth chip on the card, zero for the |
| host chip. Does not match I<SUP |
| >2</SUP |
| >C chips.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CHIP_MATCH_I2C_DRIVER</CODE |
| ></TD |
| ><TD |
| >1</TD |
| ><TD |
| >Match an I<SUP |
| >2</SUP |
| >C chip by its driver ID from the |
| <TT |
| CLASS="FILENAME" |
| >linux/i2c-id.h</TT |
| > header file.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_CHIP_MATCH_I2C_ADDR</CODE |
| ></TD |
| ><TD |
| >2</TD |
| ><TD |
| >Match a chip by its 7 bit I<SUP |
| >2</SUP |
| >C bus address.</TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8068" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >On success <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > is returned, on error <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > and the <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > variable is set appropriately:</P |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The driver does not support this ioctl, or the kernel |
| was not compiled with the <CODE |
| CLASS="CONSTANT" |
| >CONFIG_VIDEO_ADV_DEBUG</CODE |
| > |
| option, or the <CODE |
| CLASS="STRUCTFIELD" |
| >match_type</CODE |
| > is invalid, or the |
| selected chip or register does not exist.</P |
| ></DD |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EPERM</SPAN |
| ></DT |
| ><DD |
| ><P |
| >Insufficient permissions. Root privileges are required |
| to execute these ioctls.</P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
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