Re: [Astlinux-users] udev vs. hotplug

[Darrick H. (lists) <dha...@dj...>]

Kristian Kielhofner wrote:
>   devfs was never an option for AstLinux.  No way!

I never said it was.  It was a hack that needed to die sooner than it did.

>> If you're looking at this to support firmware, we need to go all the way
>> with udev.  The "hotplug" binary is NOT required with the new kernels
>> (2.6.14 and higher).  That stuff was a hack.  This page explains the
>> details farther:
>>
>> http://vrfy.org/log/recent-state-of-udev.html
>>
>> The so called "hotplug" package that is currently in trunk should be
>> removed.  It's based on something so old that it does nothing but cause
>> confusion/harm.
 >
>   I'm a little confused by this...  I am unable to find anything (nor
> have I heard of anything) that suggests firmware loading is handled
> any differently between 2.6.14 and any other kernel.  I also can't
> find anything that says its handled by the kernel at all.

I looked this up again.  I misread the comment related to 2.6.14.  The 
biggest milestone related in anyway to this discussion with that kernel 
release was the inclusion of the Intel wifi drivers.  So you are correct 
that the kernel version may not directly affect this discussion other 
than some of the events are triggered from sysfs and the way those 
triggers are created changed at some point in the kernel.

>   Just last week I had to load the firmware for a USB DSL modem I was
> playing with.  On 2.6.20 it wouldn't work with anything other than
> hotplug.  Udev probably would've worked too, if I would have bothered.
> 
>   It looks like you still need either udev or hotplug to load firmware.

Right.  udev is the more current of the two.  hotplug is no longer 
needed as udev implemented it's functionality within udev.  Look at udev 
closer.  You can (and should) have some static devices which are located 
temporarily in /lib/ then copied to /dev/ (which is mounted as tmpfs) on 
bootup.

>> I'd say we move on getting udev implemented in trunk after immediately
>> creating a 0.5 branch.  udev would then become part of 0.6.  It's a big
>> change so we should allow some time to work out the kinks.
>>
>> Darrick
> 
>   If we really need some form of hotplug for firmware loading, I'd
> rather do that pre-0.5.  We already include diethotplug - it just
> doesn't seem to actually work.  Changing from diethotplug to hotplug
> pre-0.5 and then (maybe) moving to udev later sounds best UNLESS
> firmware loading can be made to work without either.

We include diethotplug but it's not configured to do anything.  Someone 
correct me if I'm wrong, but I don't believe that the hotplug scripts 
can load the firmware without the use of udev but current releases of 
udev CAN operate without the use of the hotplug scripts.  Please note 
that the hotplug scripts are not the same as hotplug support in the 
kernel.  Hotplug support in the kernel provides the information to 
sysfs.  With current releases of udev, udevd listens for uevents sent to 
sysfs.  One of these events is the driver asking for firmware.

Darrick
-- 
Darrick Hartman
DJH Solutions, LLC
http://www.djhsolutions.com