Re: [PATCH] Fix for USB media not found at boot

On Oct 3, 2009, at 9:00 AM, Hans Petter Selasky wrote:

> On Saturday 03 October 2009 17:05:35 Scott Long wrote:
>> On Oct 3, 2009, at 4:30 AM, Hans Petter Selasky wrote:
>>> On Saturday 03 October 2009 10:19:57 Scott Long wrote:
>>>> config_intrhook system will sleep after all
>>>
>>> Then why do you need the intr hook callback?
>>
>> The config_intrhook lets you know that interrupts are enabled, the
>> scheduler is running, and mountroot hasn't run yet.  It provides a
>> very convenient and standard way to do exactly what we want with USB
>> enumeration.
>
> Hi,
>
> The root HUB attach and explore code is already running from a  
> separate
> thread, so won't that be superfluous? I mean, the HUB explore code  
> for any USB
> HUB will not run until the scheduler is running anyway.
>
> In my opinion delaying the system until the boot disk is present is  
> just not
> good. We should rather be event driven, so that every time a new  
> disk becomes
> present it checks it for mountroot.
>
> while (1) {
>       if (mountroot is successful)
>           break;
>       if (ctrl+c is pressed)
>           manual_mountroot();
>       printf("Waiting 1 second for root-disk to appear. Press CTRL+C  
> to
> abort.\n");
> 	   sleep(1);
> }

Yes.

The mount root code should keep a list of potential root devices to  
try and
it should try a device as soon as it appears. The current approach to  
block
the root mount simply because we want everything to be discovered  
before we
try to mount the root is preventing fast boots -- such as when the  
root is
a memory disk and you don't need to wait for anything...

Put differently: it's rather odd to hold off the root mount when the  
root
device is already present...

An approach like this also allows one to indefinitely wait for the root
device, which is a good feature to have...

-- 
Marcel Moolenaar
xcllnt_at_mac.com