Am 21.12.2009 um 22:30 schrieb Christoffer Dall <cd2436 at columbia.edu>: > Hi there. > > I managed to use the patch suggested by Baruch Siach on the arm-linux > mailing list to get an early console output: > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=93fd03a8c6728b58879f8af20ffd55d9c32a778b > > Eventually, I tracked down that the initcalls problem was simply that > the kernel was configured to update the LEDs on timer interrupt and > ended up sitting in a tight loop waiting for a device to respond, > which wasn't there. Configuring the kernel without LED timers solved > that issue. Oh? Why does the same kernel work in qemu then? > > Then I encountered some "wait for interrupt" instructions, which I am > so far handling by simply calling schedule() until there's a a signal > to QEMU and QEMU injects an interrupt into the guest. I'm thinking > that I'll need to do something more clever here, which will actually > cause the process itself to wait for signal, but this is a quick hack > for now. That sounds very close to the hlt instruction on x86. PPC has different SPRs that can set the CPU in a similar mode. Just look at the other architectures. There's a pretty cool helper to sleep until a signal / timer occurs. > > Finally, all the initcalls go through (although no with the best > performance), and I end up with the "Warning: Unable to open an > initial console" error message. > > The reason is that /dev/console is not there. I looked into the > initrd, and sure enough, there are no devices in there. Curiously, > using the same kernel with the same disk image on QEMU without KVM > gives a console just fine. The kernel gets "console=ttyAMA0" as > command line parameter. I can also see that the UART > > I am trying to track down when the /dev/console should be created, but > if someone on this list can clarify these questions, it will probably > save me much time: > - Is /dev/console supposed to be created in the initrd, by the init > process, by the kernel or a combination thereof? A combination. The actual device is created by the kernel. The device node on your initrd fs is just a device node. /linuxrc should create that one. > - If created by the kernel, who takes care of this? > - How is /dev/console linked to /dev/ttyXXXX? Usually using console=xxx on the kernel command line. Some distributions also ship tools to redirect the output (blogd). In your case I guess the kernel couldn't find the specified device to link /dev/console to. Double-check that the uart init code was successful. Alex
