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><A
NAME="HW"
></A
>3. Enabling Support for Your Bt8x8 Hardware in Linux</H1
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="DRIVER-INTRO"
></A
>3.1. The Bttv Driver</H2
><P
>Drivers for Bt8x8-based hardware have been a part of the <A
HREF="http://www.kernel.org/"
TARGET="_top"
>Linux</A
>
<A
HREF="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29"
TARGET="_top"
>kernel</A
> since version 2.2.0,
and are likely to be already enabled in your running kernel if you have not recompiled or
otherwise replaced your system's stock kernel with a custom version. If unavailable, Bt8x8 support can
be enabled two ways: </P
><P
><P
></P
><UL
><LI
><P
>by recompiling your kernel using the source code using
downloaded kernel-source from your distribution or fetched directly from
<A
HREF="http://www.kernel.org"
TARGET="_top"
>the kernel source repository</A
></P
></LI
><LI
><P
>the Bttv driver can be fetched directly from <A
HREF="http://bytesex.org/bttv.html"
TARGET="_top"
> the Bttv home page</A
> and then patching your available kernel source, which
should only be necessary if you have a kernel version prior to 2.2.0 or later than 2.0.35;
earlier versions are not likely to work.</P
></LI
></UL
></P
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="KERNEL-MODULES"
></A
>3.1.1. Module or In-Kernel?</H3
><P
>It is likely the stock kernel that was installed on your Linux system, if unmodified, already
supports Bt8x8-based hardware. The driver will exist either as a
loadable module or within the already running kernel. An easy way to tell is to use the
<B
CLASS="COMMAND"
>dmesg</B
> command piped into <B
CLASS="COMMAND"
>less</B
> (for easy viewing)
to look for an acknowledgement that the
driver in question was loaded when your system started up:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> $ dmesg | less</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>...which may yield something like the following, depending on your exact Bt8x8
chipset features and kernel version (in this case, 2.6):</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> Jan 26 19:40:04 localhost kernel: bttv: driver version 0.9.15 loaded
Jan 26 19:40:04 localhost kernel: bttv: using 8 buffers with 2080k
(520 pages) each for capture
Jan 26 19:40:04 localhost kernel: bttv: Bt8xx card found (0).
Jan 26 19:40:04 localhost kernel: ACPI: PCI interrupt 0000:02:09.0[A] ->
GSI 17 (level, low) -> IRQ 17
Jan 26 19:40:04 localhost kernel: bttv0: Bt878 (rev 2) at 0000:02:09.0,
irq: 17, latency: 32, mmio: 0xe7000000
Jan 26 19:40:04 localhost kernel: bttv0: detected: Hauppauge WinTV
[card=10], PCI subsystem ID is 0070:13eb
Jan 26 19:40:04 localhost kernel: bttv0: using: Hauppauge (bt878) [card=10,
autodetected]
Jan 26 19:40:04 localhost kernel: bttv0: using tuner=2
Jan 26 19:40:04 localhost kernel: tuner: chip found at addr 0xc2 i2c-bus
bt878 #0 [sw]
Jan 26 19:40:04 localhost kernel: tuner: type set to 2 (Philips NTSC
(FI1236, FM1236 and compatibles)) by bt878 #0 [sw]</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>If you don't see it, the particular driver module you are interested in may
be available but not necessarily loaded at that time. If you know what the module is named,
try using <TT
CLASS="FILENAME"
>find</TT
>; in this example we are looking for the 'bttv' module:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> $ find /lib/modules -name bttv.o</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>Note that up until the 2.4 series modules had the suffix <TT
CLASS="FILENAME"
>.o</TT
>; for 2.6+ series kernels this was replaced with <TT
CLASS="FILENAME"
>.ko</TT
>.</P
><P
>You can get a list of all modules available by typing the following at the command line:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
>
$ ls -R /lib/modules/`uname -r`/kernel </PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> Where <B
CLASS="COMMAND"
>`uname -r`</B
>, surrounded by forward tick marks, is your kernel version number.
The following output is an example of what you might find in a Bttv-ready kernel, where everything is
loaded as a module (edited for brevity):</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> /lib/modules/2.6.8/kernel/drivers/media/video:
btcx-risc.ko ir-kbd-i2c.ko tda9875.ko tvaudio.ko video-buf.ko
bttv.ko msp3400.ko tda9887.ko v4l1-compat.ko videodev.ko
ir-kbd-gpio.ko tda7432.ko tuner.ko v4l2-common.ko</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>Again, your output may vary by the currently running kernel capabilities.</P
><P
>Once you know which module your hardware needs you can find out if it is already loaded
by typing at the command line or in a terminal window:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # lsmod</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> As shown by the prompt above, you will need to have root privileges
to do this.
You should get output similar to, but not necessarily limited to the following:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> snd_bt87x 11400 0
tuner 18832 0
tvaudio 20428 0
msp3400 22100 0
bttv 145804 0
video_buf 17476 1 bttv
i2c_algo_bit 8904 1 bttv
v4l2_common 4928 1 bttv
videodev 7232 2 quickcam,bttv</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> Most stock kernels are compiled with <TT
CLASS="FILENAME"
>kmod</TT
>,
which enables automatic loading of necessary modules when the appropriate
hardware is detected. It may not always do so, however, so if you don't
have the particular module you're seeking loaded and
you think the module may be available, try loading
it manually with <B
CLASS="COMMAND"
>modprobe</B
>, as in the
following example (using the <TT
CLASS="FILENAME"
>bttv</TT
> module):</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # modprobe -v bttv</PRE
></FONT
></TD
></TR
></TABLE
></P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="RECOMPILE"
></A
>3.2. No Bttv module or in-kernel support found?</H2
><P
>If your running kernel or precompiled distribution kernel inexplicably
doesn't have Bt8x8 support enabled or available, your can always acquire new
kernel source code from the Linux <A
HREF="http://www.kernel.org"
TARGET="_top"
>kernel.org</A
> source code repository. If you are unfamiliar with the
prerequisites and procedure of compiling your own kernel, I direct you to the <A
HREF="http://www.tldp.org/HOWTO/Kernel-HOWTO.html"
TARGET="_top"
>Kernel HOWTO</A
>
for more information. </P
><P
>If you do recompile, the Bttv driver itself will obviously need to be enabled,
and is found in the heading entitled "Multimedia Devices" -> "Video for Linux"
in the 2.4 and earlier kernels in menuconfig or xconfig, or alternatively in
"Device Drivers" -> "Multimedia Devices" -> "Video for Linux" -> "BT848 Video
For Linux" in the 2.6+ series. </P
><DIV
CLASS="NOTE"
><P
></P
><TABLE
CLASS="NOTE"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="../images/note.gif"
HSPACE="5"
ALT="Note"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>You will need <TT
CLASS="FILENAME"
>i2c</TT
> subsystem support
enabled as well as <TT
CLASS="FILENAME"
>i2c-algo-bit</TT
>.</P
></TD
></TR
></TABLE
></DIV
><P
>Device support (<TT
CLASS="FILENAME"
>i2c-dev</TT
>) is not required for Bt8x8
support. Earlier than kernel version 2.3.34 i2c is not present in the kernel
source and a patch must be fetched and applied to your source, found at the
<A
HREF="http://secure.netroedge.com/~lm78/download.html"
TARGET="_top"
>lm_sensors homepage</A
>.</P
><P
>If you are running a 2.4 series kernel, <B
CLASS="COMMAND"
>btaudio</B
>
in the OSS "Sound" category is optional if you want to use external speakers
attached to the the card's audio out jack, and either (or both) OSS or
ALSA sound system btaudio drivers in the 2.6+ series.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="TUNING"
></A
>3.3. Configuration Requirements for Use of your Bttv Hardware</H2
><P
>Once you know your kernel is enabled you can proceed to some minor tuning that
may already be done for you depending on your system and distributor and
distribution features.</P
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="DEV"
></A
>3.3.1. Device Files</H3
><P
>If you are using
<A
HREF="http://www.atnf.csiro.au/people/rgooch/linux/docs/devfs.html"
TARGET="_top"
>Device Filesystem</A
> (devfs) or
<A
HREF="http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html"
TARGET="_top"
>udev</A
> your work in this respect may be done for you dynamically, but
at the same time the devices may not exist until they are recognized by the
kernel (i.e., the necessary modules loaded), so be sure you have taken care
of the previously outlined prerequisites first.</P
><P
>The Linux kernel requires a virtual device node be created to access
and control a particular piece of hardware. This node may have already been
created for you automatically; <B
CLASS="COMMAND"
>ls -l /dev/video*</B
> (with an
asterisk) or alternatively <B
CLASS="COMMAND"
>find /dev -name video*</B
> or even
visual inspection of the <TT
CLASS="FILENAME"
>/dev</TT
> directory with your
favorite file manager can give you an idea if the video devices exist. If
so you can proceed to <A
HREF="hw.html#PERMISSIONS"
>Section 3.4</A
>; if not you will need to
create them manually.</P
><P
>An easy way to create them, if available with your Linux distribution,
is use of the <TT
CLASS="FILENAME"
>MAKEDEV</TT
> script, which may be located in
<TT
CLASS="FILENAME"
>/dev</TT
> or the usual places for storing executable commands
(<TT
CLASS="FILENAME"
>/bin</TT
>,<TT
CLASS="FILENAME"
>/sbin</TT
> and so on). The manual
page for <TT
CLASS="FILENAME"
>MAKEDEV</TT
> (<B
CLASS="COMMAND"
>man MAKEDEV</B
>) can
guide you further, but be aware of the device-specific command options. If
<TT
CLASS="FILENAME"
>MAKEDEV</TT
> doesn't work or doesn't exist, or you just prefer
doing things the hard way, move on to the next paragraph.</P
><P
>A device can be created as a block (such as a drive), a FIFO
(file-in-file-out or pipe, as in xconsole) or a character device, which
represents other hardware.
Each device has a major and a minor number <SPAN
CLASS="QUOTE"
>"coordinate"</SPAN
>
to tell the kernel what it is and where to access it.
These numbers are not arbitrary. The major number 81 with minor number 0, 1,
2, and so on are by convention assigned to Video4linux devices, including TV
tuner boards and webcams. In order to create the video device
<TT
CLASS="FILENAME"
>/dev/video0</TT
>, use <B
CLASS="COMMAND"
>mknod</B
> at the command
line:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # mknod /dev/video0 c 81 0</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>where <B
CLASS="COMMAND"
>c</B
> represents a character device.</P
><P
> You can use the following script, which I
have borrowed from the kernel source (located in
<TT
CLASS="FILENAME"
>linux/Documentation/video4linux/bttv/MAKEDEV</TT
> of
the source tree):</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> #!/bin/bash
function makedev () {
for dev in 0 1 2 3; do echo "/dev/$1$dev:
char 81 $[ $2 + $dev ]" rm -f /dev/$1$dev
mknod /dev/$1$dev c 81 $[ $2 + $dev ] chmod
666 /dev/$1$dev
done
# symlink for default device
rm -f /dev/$1 ln -s /dev/${1}0 /dev/$1
}
# see http://roadrunner.swansea.uk.linux.org/v4lapi.shtml
echo "*** new device names ***" makedev video
0 makedev radio 64 makedev vtx 192 makedev vbi 224
# "*** old device names (for compatibility only) ***"
#makedev bttv 0 #makedev bttv-fm 64 #makedev bttv-vbi 224</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> Simply copy and paste the above into your favorite editing program,
save it as MAKEDEV or whatever name you like, make it executable
(i.e., <B
CLASS="COMMAND"
>chmod u+x MAKEDEV</B
>), and then execute it as root: </P
><P
> <TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # ./MAKEDEV</PRE
></FONT
></TD
></TR
></TABLE
></P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="PERMISSIONS"
></A
>3.4. Groups and Permissions</H2
><P
> It is a good idea to be sure that your user account can access
the device once all modules are loaded and device nodes created.
The most security-conscious way to do that is to add access for a
particular group.
On my system, the members of the group 'video' are allowed to use the
webcam, scanner and other photographic devices.
The way to accomplish this is to first change the ownership of the
devices in <TT
CLASS="FILENAME"
>/dev</TT
> like so (as root): </P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # chown root.video /dev/usb/video*</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> ...where <B
CLASS="COMMAND"
>root.video</B
> are the owner and group
the device will now belong to.
Obviously, the specific command will vary by your system and the type
of device.
It is important that you change the ownership of the device node itself
and not the symlink; symlinks' ownerships are affected only by changing
the parent devices or files they point to. </P
><P
> To see if your user account is a member of the group in question,
as root issue the following command:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # grep -e video /etc/group</PRE
></FONT
></TD
></TR
></TABLE
>
You should see something like the following:</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> video:x:44:</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> ...where '44' is the group number.
Since no members follow the last colon in the 'video' group, we can add
them, let's say user 'jhs' with the command</P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # adduser jhs video</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> After this, it's simply a matter of allowing read and write access
for the user in question of the device like so: </P
><P
><TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> # chmod g+rw /dev/v4l/video0</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
> ...where <B
CLASS="COMMAND"
>g+rw</B
> means add <B
CLASS="COMMAND"
>r</B
>ead
and <B
CLASS="COMMAND"
>w</B
>rite access for <B
CLASS="COMMAND"
>g</B
>roup.
See the documentation for chmod (<B
CLASS="COMMAND"
>man chmod</B
> or
<B
CLASS="COMMAND"
>info chmod</B
>) for further info.</P
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