Re: [Devil-Linux-discuss] How to switch on blacklisting in new udev?

[Andrzej O. <an...@ma...>]

Heiko Zuerker wrote:
> the new udev doesn't use the module-init-tools anymore.
> They have switch to kmod, which is a library.
> 
> Maybe the kmod sources have some information.

Heiko,

I apologize for the delay - I was sick. Thanks for suggestions. Indeed, I read 
that from the version 171 of udev does not use the m-i-t but kmod library 
directly. But the preliminary analysis of the sources shows that blacklist is 
treated differently in m-i-t and in kmod, and that it is rather a political 
decision. It seems that for kmod dependencies are stronger than the blacklist. 
So the whole philosophy of loading dahdi drivers modules for Asterisk 
telephony cards out the window.

Since each telephony card typically provides a number of channels and these 
are numbered, it is not irrelevant, in what order we load the cards drivers. 
Therefore, the Asterisk developers recommend that all drivers should be on the 
modprobe blacklist and then loaded on demand by init.d script in the desired 
order. This worked with old udev and m-i-t correctly.

Meanwhile, the presence of telephony card is treated as a dependency and 
udev/kmod loads drivers regardless of their presence on a blacklist in 
/etc/modprobe.d/modprobe.conf. Loads them automatcally in the order of cards 
on the bus and not in the order desired because of the numbers of telephone 
channels. The behavior of udev/kmod is relatively young and not present in 
many distribution.

This is strange kmod blacklist policy, where the blacklist is not a blacklist, 
but the discussion shows that the kmod authors rather insist on his own.

Of course we can patch the kmod, but it has a little sense because it is the 
political behavior so patch would be branch from main line of development. We 
need wait for further decisions: whether Digium becomes independent on the 
order of loading drivers or kmod team will change the blacklisting policy. So 
now is the easiest way to get around the problem by modifying the script 
/etc/init.d/dahdi to mandatory unload all telephony cards drivers before 
loading they in desired order. And drivers would be loaded, unloaded and 
loaded again.

Best Regards

-- 
Andrzej Odyniec