Silly udev script [was Re: udev and devfs - The final word]

Silly udev script [was Re: udev and devfs - The final word]

[Greg KH]

On Mon, Jan 05, 2004 at 08:13:26AM -0800, Linus Torvalds wrote:
> 
> For example, if you wanted to, you could make udev do a cddb lookup on the
> CD-ROM, and use that as the pathname, so that when you insert your
> favorite audio disk, it will always show up in the same place, regardless 
> of whether you put it in the DVD slot or the CD-RW drive. 
> 
> [ Yeah, that sounds like a singularly silly thing to do, but it's a good 
>   example of something where there is no actual serial number, but you can 
>   "identify" it automatically through its contents, and name it stably 
>   according to that. ]

That was such a silly thing to do, here's a script that does it, along
with the udev rule to add to udev.rules for it.  It names your cdrom
Artist_Title, and creates a symlink called cdrom that points to it, just
to be a tiny bit sane :)

I had been saying for a long time that you could have udev make a query
across the network to get a device name, this provides the perfect
example of just that...

thanks,

greg k-h


#!/usr/bin/perl

# a horribly funny script that shows how flexible udev can really be
# This is to be executed by udev with the following rules:
# CALLOUT, BUS="ide", PROGRAM="name_cdrom.pl %M %m", ID="good*", NAME="%1c", SYMLINK="cdrom" 
# CALLOUT, BUS="scsi", PROGRAM="name_cdrom.pl %M %m", ID="good*", NAME="%1c", SYMLINK="cdrom" 
#
# The scsi rule catches USB cdroms and ide-scsi devices.
#

use CDDB_get qw( get_cddb );

my %config;

$dev_node = "/tmp/cd_foo";

# following variables just need to be declared if different from defaults
$config{CDDB_HOST}="freedb.freedb.org";        # set cddb host
$config{CDDB_PORT}ˆ80;                       # set cddb port
$config{CDDB_MODE}="cddb";			# set cddb mode: cddb or http
$config{CD_DEVICE}="$dev_node";			# set cd device

# No user interaction, this is a automated script!
$config{input}=0;

$major = $ARGV[0];
$minor = $ARGV[1];

# create our temp device node to read the cd info from
if (system("mknod $dev_node b $major $minor")) {
       die "bad mknod failed";
       }

# get it on
my %cd=get_cddb(\%config);

# remove the dev node we just created
unlink($dev_node);

# print out our cd name if we have found it
unless(defined $cd{title}) {
	print"bad unknown cdrom\n";
} else {
	print "good $cd{artist}_$cd{title}\n";
}


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Re: Silly udev script [was Re: udev and devfs - The final word]

[Kay Sievers]

[-- Attachment #1: Type: text/plain, Size: 1066 bytes --]

On Mon, Jan 05, 2004 at 04:36:14PM -0800, Greg KH wrote:
> On Mon, Jan 05, 2004 at 08:13:26AM -0800, Linus Torvalds wrote:
> > [ Yeah, that sounds like a singularly silly thing to do, but it's a good 
> >   example of something where there is no actual serial number, but you can 
> >   "identify" it automatically through its contents, and name it stably 
> >   according to that. ]
> 
> That was such a silly thing to do, here's a script that does it, along
> with the udev rule to add to udev.rules for it.  It names your cdrom
> Artist_Title, and creates a symlink called cdrom that points to it, just
> to be a tiny bit sane :)

Hey, this is funny.
I couldn't resist to give it a try and we need a few changes:

  - it's %2c otherwise nearly all my CD's are "good", but sure I also have bad ones :)
  - remove the node first, cause get_cddb() dies and leaves the old one there
  - remove spaces in name, cause this is our separator

/udev/
|-- The_Cure-The_Peel_Sessions
|-- cdrom -> ./The_Cure-The_Peel_Sessions
|-- hda
|-- hda1
|-- hda2
|-- hda4

thanks,
Kay

[-- Attachment #2: 01-cddb-name.diff --]
[-- Type: text/plain, Size: 1201 bytes --]

--- ../udev/extras/name_cdrom.pl	2004-01-06 04:15:31.000000000 +0100
+++ extras/name_cdrom.pl	2004-01-06 04:34:45.000000000 +0100
@@ -2,8 +2,8 @@
 
 # a horribly funny script that shows how flexible udev can really be
 # This is to be executed by udev with the following rules:
-# CALLOUT, BUS="ide", PROGRAM="name_cdrom.pl %M %m", ID="good*", NAME="%1c", SYMLINK="cdrom" 
-# CALLOUT, BUS="scsi", PROGRAM="name_cdrom.pl %M %m", ID="good*", NAME="%1c", SYMLINK="cdrom" 
+# CALLOUT, BUS="ide", PROGRAM="name_cdrom.pl %M %m", ID="good*", NAME="%2c", SYMLINK="cdrom"
+# CALLOUT, BUS="scsi", PROGRAM="name_cdrom.pl %M %m", ID="good*", NAME="%2c", SYMLINK="cdrom"
 #
 # The scsi rule catches USB cdroms and ide-scsi devices.
 #
@@ -27,9 +27,10 @@
 $minor = $ARGV[1];
 
 # create our temp device node to read the cd info from
+unlink($dev_node);
 if (system("mknod $dev_node b $major $minor")) {
        die "bad mknod failed";
-       }
+}
 
 # get it on
 my %cd=get_cddb(\%config);
@@ -41,5 +42,7 @@
 unless(defined $cd{title}) {
 	print"bad unknown cdrom\n";
 } else {
-	print "good $cd{artist}_$cd{title}\n";
+	$cd{artist} =~ s/ /_/g;
+	$cd{title} =~ s/ /_/g;
+	print "good $cd{artist}-$cd{title}\n";
 }

Re: Silly udev script [was Re: udev and devfs - The final word]

[Greg KH]

On Tue, Jan 06, 2004 at 05:02:34AM +0100, Kay Sievers wrote:
> On Mon, Jan 05, 2004 at 04:36:14PM -0800, Greg KH wrote:
> > On Mon, Jan 05, 2004 at 08:13:26AM -0800, Linus Torvalds wrote:
> > > [ Yeah, that sounds like a singularly silly thing to do, but it's a good 
> > >   example of something where there is no actual serial number, but you can 
> > >   "identify" it automatically through its contents, and name it stably 
> > >   according to that. ]
> > 
> > That was such a silly thing to do, here's a script that does it, along
> > with the udev rule to add to udev.rules for it.  It names your cdrom
> > Artist_Title, and creates a symlink called cdrom that points to it, just
> > to be a tiny bit sane :)
> 
> Hey, this is funny.
> I couldn't resist to give it a try and we need a few changes:
> 
>   - it's %2c otherwise nearly all my CD's are "good", but sure I also have bad ones :)
>   - remove the node first, cause get_cddb() dies and leaves the old one there
>   - remove spaces in name, cause this is our separator

Doh, that's what I get for only trying it with a 1 word title cd, and
then adding error code after testing it...

Thanks, I've applied your fixes.

greg k-h


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