[Buildroot] /dev/ttyS0 in filesystem created by Buildroot can't be opened in Qemu

[Baruch Siach <baruch@tkos.co.il>]

Hi Mihajlo,

On Tue, Jul 10, 2012 at 12:22:02PM +0200, Mihajlo Jovanovi? wrote:
> Actually, I had to change the command to
> 
> qemu-system-arm -M vexpress-a9 -kernel output/images/zImage -drive
> file=output/images/rootfs.ext2,if=sd -append "console=ttyAMA0,115200
> root=/dev/mmcblk0 rw " -serial stdio -net nic,model=lan9118 -net user
> 
> otherwise ext2 was read only, and I got messages that /dev/null and
> /dev/ttyAMA0 can not be open.

Whether or not the root filesystem is mounted read-only should not affect the 
functionality of device nodes. There seems to be some other problem here.

> However, now when I launch Qemu it freezes while starting network:
> 
>  Freeing init memory: 172K
> 
> Starting logging: OK
> 
> Starting mdev...
> 
> Starting network...
> 
> It just waits there until I terminate it. I have recompiled the kernel and
> deactivate networking as I really don't need it now, but without success.
> It just printed an additional message that sockets are not implemented.

Did you make a clean build after changing the configuration? The Buildroot 
configuration system can't detect all configuration changes so sometimes you 
must start from clean. Specifically, make sure that your /etc/inittab has the 
right getty command with ttyAMA0.

baruch

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