udev considerations: usb-storage script and $REMOVER problem

udev considerations: usb-storage script and $REMOVER problem

[Pedro Alves]

Hi.


I use kernel 2.6.11, udev 054 and hotplug-2004_09_23.


My hotplug scripts for a digital camera (usb-storage) worked well in 2.4.x
series, but stoped working in 2.6. Yesterday I put my mind in trying to
figure out what the problem was. Its not the kernel but udev.


I have a /etc/hotplug/usb/my.usermap file for my camera, that executes a
script that mounts the storage device and places a link from $REMOVER env
var to a script that simply unmounts the storage device.


The problem was that when usb.agent executed the script, udev had not yet
created the device and mount failed. 


Since I suck at bash scripting, I made a simple ugly-but-working-script
that checks if the device exists and executes the commands. Also has a
retry time out. 


Would be nice if hotplug could handle this management somehow...

________________________________

#!/usr/bin/perl -w

system "logger -t Hotplug Mounting Fuji";

my $ret = 0;
my $retry = 0;

while ($retry < 10 && !$ret ){
    if ( -e '/dev/sda1' ){
        $ret = 1
    }
    else{
        system "logger ...sleeping $retry";
        sleep 1;
        $retry++;
    }
}

if ( $ret ){

    system "mount /mnt/fuji-f401";
    system "logger -t Hotplug REMOVER script: $ENV{REMOVER}";
    system "ln -s /etc/hotplug/usb/fuji401-remove $ENV{REMOVER}";

}
else{
    system "logger Fuji mount script failed";
}
________________________________



Afterwards, the mount script worked ok. But when I turned off the camera,
the shutdown script didn't. Digging a bit more I found that the error was
here:

REMOVER=/var/run/usb/$(readlink -f $SYSFS/$DEVPATH | sed -e 's;/;%;g')

Since udev removed the device from the system before the hotplug executed
the script, readlink returned an empty string and the script was not found.


I changed this line to:

REMOVER=/var/run/usb/$(echo $SYSFS/$DEVPATH | sed -e 's;/;%;g')

and now all works ok. 


I saw in the mailing list some references to this readlink problem, but
was not clear to me if this was a bug or a feature.


Hope this helps.


Thanks

-- 
Pedro Alves
pedro.alves@zmail.pt


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