Re: [linux-usb-devel] PROBLEM: when booting from USB-HDD device kernel 2.4.21 is trying to mount root file system too early before usb device is found on the usb-bus

[David Brownell <david-b@pacbell.net>]

Ilia A. Petrov wrote:
> David Brownell wrote:
>> Ilia A. Petrov wrote:
>>
>>> When kernel is mounting root file system it is doing it too fast so 
>>> usb-support have not ime to scan bus for mass-storage devices and 
>>> connect them.
>>> ...
>>> or, imho better way, - when completing init of usb bus, first scans 
>>> it and connect all devices and only after all devices were connected 
>>> returns to main kernel code.
>>
>>
>>
>> That might not entirely solve the problem, since the relevant device
>> could drop off the bus temporarily, but it seems like it'd be a step
>> forward.  How would you make root hub ("bus") initialization do that?
> 
> 
> i'm not familiar with linux usb implementation so may be it's wrong:
> after sending global reset over the bus you can manually check (not 
> trough the hub driver) root port connection status and call enumeration 
> if needed.

I had in mind an explanation that works with "patch -p1" ... :)

There's already a call to register a root hub.  It'd be dangerous
to have some other thread try to share responsibilities with khubd,
so that call would likely need to be modified.  (Although there's
been a bit of discussion about actually getting rid of that specific
single-point-of-failure, since not all hub operations need to be
serialized.)

- Dave