Re: Rationale for delay_use in USB storage?

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Mon, 26 Nov 2007, Mike Nuss wrote:

> I'm using a USB Mass Storage flash device to boot on an embedded
> system and I'm trying to reduce the boot time as much as possible. One
> delay I'm encountering is the "Waiting for device to settle" delay
> after the kernel detects the mass storage device.  I see that this is
> controlled by the delay_use parameter in usb-storage but I couldn't
> find any documentation as to why a device would need to settle.  Could
> someone explain?

Not really.  All we know is that some devices (some Apple iPods, for
example) really do seem to need it.  That is, with the delay they work
and without it they don't work.

5 seconds is overkill in all likelihood, but we wanted the default to 
work as widely as possible.  You can, of course, always set the module 
parameter to 0.

Alan Stern


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