| <refentry id="vidioc-dbg-g-register"> |
| <refmeta> |
| <refentrytitle>ioctl VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER</refentrytitle> |
| &manvol; |
| </refmeta> |
| |
| <refnamediv> |
| <refname>VIDIOC_DBG_G_REGISTER</refname> |
| <refname>VIDIOC_DBG_S_REGISTER</refname> |
| <refpurpose>Read or write hardware registers</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <funcsynopsis> |
| <funcprototype> |
| <funcdef>int <function>ioctl</function></funcdef> |
| <paramdef>int <parameter>fd</parameter></paramdef> |
| <paramdef>int <parameter>request</parameter></paramdef> |
| <paramdef>struct v4l2_dbg_register *<parameter>argp</parameter></paramdef> |
| </funcprototype> |
| </funcsynopsis> |
| <funcsynopsis> |
| <funcprototype> |
| <funcdef>int <function>ioctl</function></funcdef> |
| <paramdef>int <parameter>fd</parameter></paramdef> |
| <paramdef>int <parameter>request</parameter></paramdef> |
| <paramdef>const struct v4l2_dbg_register |
| *<parameter>argp</parameter></paramdef> |
| </funcprototype> |
| </funcsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Arguments</title> |
| |
| <variablelist> |
| <varlistentry> |
| <term><parameter>fd</parameter></term> |
| <listitem> |
| <para>&fd;</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><parameter>request</parameter></term> |
| <listitem> |
| <para>VIDIOC_DBG_G_REGISTER, VIDIOC_DBG_S_REGISTER</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><parameter>argp</parameter></term> |
| <listitem> |
| <para></para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <note> |
| <title>Experimental</title> |
| |
| <para>This is an <link linkend="experimental">experimental</link> |
| interface and may change in the future.</para> |
| </note> |
| |
| <para>For driver debugging purposes these ioctls allow test |
| applications to access hardware registers directly. Regular |
| applications must not use them.</para> |
| |
| <para>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 <constant>CONFIG_VIDEO_ADV_DEBUG</constant> option |
| to enable these ioctls.</para> |
| |
| <para>To write a register applications must initialize all fields |
| of a &v4l2-dbg-register; and call |
| <constant>VIDIOC_DBG_S_REGISTER</constant> with a pointer to this |
| structure. The <structfield>match.type</structfield> and |
| <structfield>match.addr</structfield> or <structfield>match.name</structfield> |
| fields select a chip on the TV |
| card, the <structfield>reg</structfield> field specifies a register |
| number and the <structfield>val</structfield> field the value to be |
| written into the register.</para> |
| |
| <para>To read a register applications must initialize the |
| <structfield>match.type</structfield>, |
| <structfield>match.addr</structfield> or <structfield>match.name</structfield> and |
| <structfield>reg</structfield> fields, and call |
| <constant>VIDIOC_DBG_G_REGISTER</constant> with a pointer to this |
| structure. On success the driver stores the register value in the |
| <structfield>val</structfield> field. On failure the structure remains |
| unchanged.</para> |
| |
| <para>When <structfield>match.type</structfield> is |
| <constant>V4L2_CHIP_MATCH_BRIDGE</constant>, |
| <structfield>match.addr</structfield> selects the nth non-sub-device 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-INFO; ioctl.</para> |
| |
| <para>When <structfield>match.type</structfield> is |
| <constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant>, |
| <structfield>match.name</structfield> contains the I2C driver name. |
| For instance |
| <constant>"saa7127"</constant> 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-INFO; ioctl you can find out which &i2c; chips are |
| present.</para> |
| |
| <para>When <structfield>match.type</structfield> is |
| <constant>V4L2_CHIP_MATCH_I2C_ADDR</constant>, |
| <structfield>match.addr</structfield> selects a chip by its 7 bit &i2c; |
| bus address.</para> |
| |
| <para>When <structfield>match.type</structfield> is |
| <constant>V4L2_CHIP_MATCH_AC97</constant>, |
| <structfield>match.addr</structfield> selects the nth AC97 chip |
| on the TV card.</para> |
| |
| <para>When <structfield>match.type</structfield> is |
| <constant>V4L2_CHIP_MATCH_SUBDEV</constant>, |
| <structfield>match.addr</structfield> selects the nth sub-device.</para> |
| |
| <note> |
| <title>Success not guaranteed</title> |
| |
| <para>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-INFO; |
| call confirming the presence of the selected &i2c; chip.</para> |
| </note> |
| |
| <para>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-INFO;. Conversely it may support |
| <constant>VIDIOC_DBG_G_CHIP_INFO</constant> but not these ioctls.</para> |
| |
| <para><constant>VIDIOC_DBG_G_REGISTER</constant> and |
| <constant>VIDIOC_DBG_S_REGISTER</constant> were introduced in Linux |
| 2.6.21, but their API was changed to the one described here in kernel 2.6.29.</para> |
| |
| <para>We recommended the <application>v4l2-dbg</application> |
| utility over calling these ioctls directly. It is available from the |
| LinuxTV v4l-dvb repository; see <ulink |
| url="http://linuxtv.org/repo/">http://linuxtv.org/repo/</ulink> for |
| access instructions.</para> |
| |
| <!-- Note for convenience vidioc-dbg-g-chip-ident.sgml |
| contains a duplicate of this table. --> |
| <table pgwide="1" frame="none" id="v4l2-dbg-match"> |
| <title>struct <structname>v4l2_dbg_match</structname></title> |
| <tgroup cols="4"> |
| &cs-ustr; |
| <tbody valign="top"> |
| <row> |
| <entry>__u32</entry> |
| <entry><structfield>type</structfield></entry> |
| <entry>See <xref linkend="ident-chip-match-types" /> for a list of |
| possible types.</entry> |
| </row> |
| <row> |
| <entry>union</entry> |
| <entry>(anonymous)</entry> |
| </row> |
| <row> |
| <entry></entry> |
| <entry>__u32</entry> |
| <entry><structfield>addr</structfield></entry> |
| <entry>Match a chip by this number, interpreted according |
| to the <structfield>type</structfield> field.</entry> |
| </row> |
| <row> |
| <entry></entry> |
| <entry>char</entry> |
| <entry><structfield>name[32]</structfield></entry> |
| <entry>Match a chip by this name, interpreted according |
| to the <structfield>type</structfield> field.</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </table> |
| |
| |
| <table pgwide="1" frame="none" id="v4l2-dbg-register"> |
| <title>struct <structname>v4l2_dbg_register</structname></title> |
| <tgroup cols="4"> |
| <colspec colname="c1" /> |
| <colspec colname="c2" /> |
| <colspec colname="c4" /> |
| <tbody valign="top"> |
| <row> |
| <entry>struct v4l2_dbg_match</entry> |
| <entry><structfield>match</structfield></entry> |
| <entry>How to match the chip, see <xref linkend="v4l2-dbg-match" />.</entry> |
| </row> |
| <row> |
| <entry>__u64</entry> |
| <entry><structfield>reg</structfield></entry> |
| <entry>A register number.</entry> |
| </row> |
| <row> |
| <entry>__u64</entry> |
| <entry><structfield>val</structfield></entry> |
| <entry>The value read from, or to be written into the |
| register.</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </table> |
| |
| <!-- Note for convenience vidioc-dbg-g-chip-ident.sgml |
| contains a duplicate of this table. --> |
| <table pgwide="1" frame="none" id="chip-match-types"> |
| <title>Chip Match Types</title> |
| <tgroup cols="3"> |
| &cs-def; |
| <tbody valign="top"> |
| <row> |
| <entry><constant>V4L2_CHIP_MATCH_BRIDGE</constant></entry> |
| <entry>0</entry> |
| <entry>Match the nth chip on the card, zero for the |
| bridge chip. Does not match sub-devices.</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_CHIP_MATCH_I2C_DRIVER</constant></entry> |
| <entry>1</entry> |
| <entry>Match an &i2c; chip by its driver name.</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_CHIP_MATCH_I2C_ADDR</constant></entry> |
| <entry>2</entry> |
| <entry>Match a chip by its 7 bit &i2c; bus address.</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_CHIP_MATCH_AC97</constant></entry> |
| <entry>3</entry> |
| <entry>Match the nth anciliary AC97 chip.</entry> |
| </row> |
| <row> |
| <entry><constant>V4L2_CHIP_MATCH_SUBDEV</constant></entry> |
| <entry>4</entry> |
| <entry>Match the nth sub-device.</entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </table> |
| </refsect1> |
| |
| <refsect1> |
| &return-value; |
| |
| <variablelist> |
| <varlistentry> |
| <term><errorcode>EPERM</errorcode></term> |
| <listitem> |
| <para>Insufficient permissions. Root privileges are required |
| to execute these ioctls.</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| </refentry> |