[U-Boot] Kernel patch for CONFIG_LOGBUFFER

[Evseev, Serguei]

On Monday, June 29, 2009 7:23 AM, Detlev Zundel [mailto:dzu at denx.de] wrote
> Serguei <sevseev at safenet-inc.com> wrote:
> > I'm looking for a working patch for the Linux kernel 2.6.28.8 that
> > would allow using CONFIG_LOGBUFFER (a kernel log buffer shared between
> > U-Boot and the kernel). I'm using u-boot 1.3.3. When LOGBUFFER is
> > enabled in the kernel configuration the kernel build fails with:
> > kernel/built-in.o: In function `setup_ext_logbuff': : undefined
> > reference to `setup_ext_logbuff_mem'
> 
> This is to be expected - CONFIG_LOGBUFFER only worked with arch/ppc.  It
> is broken since the arch/ppc removal and nobody (yet) cared to get it to
> life again.  Only recently there were discussions on the linux-embedded
> ml[1] which may yield other solutions going mainline.
> 
> > Could anybody also tell me how the buffer location (I think the size
> > is fixed to 16K) is communicated to the kernel, via a kernel command
> > line parameter? If so, what is it?
> 
> It was placed at a known address relative to the end of RAM.  Check
> arch/ppc/mm/init.c e.g. in our DENX-v2.6.25-stable branch.

Hi Detlev,

Thanks for the info. I've seen some discussions and proposed patches, but I thought they were mainly coming from the DENX kernel tree, where I could not locate them. Anyways, I got much better picture now. Thanks a lot.

Regards,
Serguei

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