Messages in this thread | | | Date | Fri, 28 May 2004 18:37:49 +0900 | From | Kalin KOZHUHAROV <> | Subject | Re: boot from usb flash - wake boot process when disk is ready? |
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David N. Welton wrote: > [ Please CC replies to me - thanks! ] > > Hi, > > We're toying around with the idea of booting an embedded system off of > USB flash (pros, cons, and advice about this would be appreciated, by > the way), and I had a look at several of the existing patches to do this > without going through the process of creating an initrd image. That > adds complexity and time to the boot process that we would prefer to > avoid, although it appears that the kernel folks in the first thread > cited are in favor of initrd.... > > http://www.uwsg.iu.edu/hypermail/linux/kernel/0301.3/1182.html > > This mentions a couple of patches, both the "keep looping until it > works" one, which I couldn't get working with 2.6.6, and Willy Tarreu's > "wait a given period of time before continuing" patch: > > http://www.uwsg.iu.edu/hypermail/linux/kernel/0405.0/0224.html > > I don't think either of those approaches are particularly elegant... > although I'm sure my own efforts are good for a snort as well. I tried this with 2.6.6 and modified it a bit, but to no avail. It seems that the sd driver initializes the disk long before the wait and does not bother anymore.
> In genhd.c I wake up a waitqueue when the disk comes on line. The > init process waits on this before going on with prepare_namespace(). > Ideally, this would look and make sure it's the right disk, that > selected for the root fs:-) Not being very familiar with the 'lay of > the land' in the kernel, I declared the wait queue as a global in > genhd.c. The thing I don't like about this approach is that it builds a > connection between two bits of the kernel that seem separate... maybe > (ok, quite probably) there is a better/cleaner way of doing this? > > Patch is at: http://dedasys.com/freesoftware/files/usb-wakeup.patch
Looks OK to me to try, but I am far from expert here. Unfortunately I cannot test it in the next few days :-( May be later.
I am in a search for non-initrd USB-booting as well...
Keep the discussion on LKML as well.
Kalin.
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