On Tue, Feb 17, 2009 at 08:54:24AM -0700, M. Warner Losh wrote:
> In message: <200902170856.11631.hsela...@c2i.net>
>             Hans Petter Selasky <hsela...@c2i.net> writes:
> : On Tuesday 17 February 2009, Marcel Moolenaar wrote:
> : > > But it looks like the old usb code didn't call it either...  I think
> : > > old code enumerated right away during boot, while the new code defers
> : > > the enumeration until events can be processed...
> : >
> : > Yes, you're right. USB1 used the following:
> : >
> : > SYSINIT(usb_cold_explore, SI_SUB_CONFIGURE, SI_ORDER_MIDDLE,
> : >      usb_cold_explore, NULL);
> : >
> : > SI_SUB_CONFIGURE didn't complete before all USB busses
> : > were enumerated.
> : 
> : I would really prefer that first time USB enumeration is not synchronous. 
> This 
> : has to do with startup timing. It simply wastes a lot of time to wait for 
> all 
> : the busses to be probed in serial. Sure it works nice with a USB keyboard 
> and 
> : a USB mouse, but when you have a couple of USB HUBs and +8 devices 
> connected, 
> : it simply speeds up the boot time so that you reach the root prompt by the 
> : time you would else have done the mount root mfs.
> : 
> : If the mountroot code cannot find the disk, it should sleep and loop.
> 
> I think this is a weak argument.  I'm strongly in favor of the usb1
> behavior here.

I think its slightly more complex that adding a cold explore task. Most
of the USB2 periperhel drivers defer a portion of their attach to a
thread task, a change which needs to be reverted first. As others have
said both the probe and attach must be synchronous.


Andrew
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