Bootloader

robert lazarski robertlazarski at gmail.com
Thu Mar 20 22:02:28 CET 2008


On Thu, Mar 20, 2008 at 4:21 PM, Andy Green <andy at openmoko.com> wrote:
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> > Really, why would we need any device driver in the bootloader?
>  > Bootloader are not meant to deal with the device, they let the OS do it.
>
>  We have to have a little device-specific knowledge in there to get at
>  the kernel image over SD on VFAT for example, or it seems NAND bad block
>  skipping, but it should be really really minimal.
>

At least the way I use drivers in bootloaders and in u-boot in
particular is to validate the hardware without a kernel. Once a
version u-boot is loaded, hacking various kernel versions is that much
easier. u-boot has a shell that can get deep into protocals like I2C,
SPD, CFI and many others. Memory is arguably the most tricky part in
bringing up an OS and something that the kernel expects to be ready to
go, and u-boot 's community and code is a good asset here.

>
>  > And you're right, we could write a dozen of minimal bootloaders by the
>  > same time we spend fixing/maintaining u-boot.
>
>  Well if U-Boot already came patched and working, to start with it would
>  be quicker to use it.  But I prefer to get rid of it.

By getting rid of u-boot you'd IMHO be losing one of the attractions
to openmoko: a low barrier to-entry hackable device. In my case I'm a
contributor to u-boot, knows how it works a bit, and am looking
forward to hacking it on openmoko. Writing your own bootloader or
using kexec may be interesting to some, and since its open source no
one is stopping you. But at least one other option is taking advantage
of an active and knowledgable community like uboot

As far as patches and u-boot are concerned, I talked to some people at
the recent bossa conference here in brazil and expect to see some
progress soon. I myself am waiting for the freerunner to get released,
as I don't have any hardware yet.

Cheers,
Robert




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