Re: replace dev.d/ with a rule based program execution

[Greg KH <greg@kroah.com>]

On Mon, Feb 21, 2005 at 07:12:42PM +0100, Kay Sievers wrote:
> Here is an experimental patch to replace the brute-force dev.d/ script
> execution by a rule based model, with the same logic we currently use to
> name a device. While searching for a rule to apply, we collect programs
> to execute after node creation/removal.
> 
> This makes it possible to gain complete control of the execution of programs
> for a specific device instead of letting the programs exit if they don't
> want to handle the device.
> 
> We apply the rule on device remove events too. A ACTION="<value>" match can
> be used to write rules that are only applied on a specific action.
> 
> I've replaced the following:
>   [kay@pim ~]$ tree /etc/dev.d/
>   /etc/dev.d/
>   |-- default
>   |   |-- 00-log.dev
>   |   |-- 05-pam_console.dev -> ../../udev/scripts/pam_console.dev
>   |   `-- 10-hal.dev -> /usr/libexec/hal.dev
>   |-- fd0
>   |   `-- 10-MAKEDEV.dev -> ../../udev/scripts/MAKEDEV.dev
>   |-- fd1
>   |   `-- 10-MAKEDEV.dev -> ../../udev/scripts/MAKEDEV.dev
>   |-- fd2
>   |   `-- 10-MAKEDEV.dev -> ../../udev/scripts/MAKEDEV.dev
>   |-- fd3
>   |   `-- 10-MAKEDEV.dev -> ../../udev/scripts/MAKEDEV.dev
>   `-- sound
>       `-- alsa.dev
> 
> With these rules:
>   KERNEL="ttyUSB*", HOTPLUG="<usb-serial-device program>"
>   SUBSYSTEM="tty", OPTIONS="no_hotplug"
>   SUBSYSTEM="vc", OPTIONS="no_hotplug"
> 
>   ACTION="add", SUBSYSTEM="sound", HOTPLUG="/etc/dev.d/sound/alsa.dev"
>   ACTION="add", KERNEL="fd*", HOTPLUG="/etc/udev/scripts/MAKEDEV.dev"
>   ACTION="add", HOTPLUG="/etc/udev/scripts/pam_console.dev"
> 
>   HOTPLUG="/usr/libexec/hal.dev"
>   HOTPLUG="/etc/dev.d/default/00-log.dev"
> 
> On my box, udevstart takes 2.1 seconds instead of 8.6 seconds to run with
> my default setup. Mainly because it will not run anything for all the virtual
> tty devices. Any tty device which should be catched, needs a rule before the
> "no_hotplug" option.
> 
> It is also possible to pass arguments to the scripts, which sometimes
> makes it no longer necessary to wrap a program with a shell script.

I like the general idea, but we can't break the /etc/dev.d/ functionalty
so much.

If we just add a udev option (like you show above) for "no_dev.d", we
could still have the massive udevstart speedups, right?  So this is ok
with me.

Remember, it's easier for a package to drop a symlink into the
/etc/dev.d/ directory tree, than it is for it to modify / add a udev
rule.

> We could also remove all the hardcoded knowledge about sysfs in the
> wait_for_sysfs logic and replace it by a few simple ignore_device rules.

How would that happen?

> The same model could easily replace the whole hotplug.d/ multiplexing and
> give use an efficient rule based event management with a single source of
> policy.

See my previous response as to why we can't do this.

thanks,

greg k-h


-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_ide95&alloc_id\x14396&op=click
_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel