[U-Boot] Kernel patch for CONFIG_LOGBUFFER

[U-Boot] Kernel patch for CONFIG_LOGBUFFER

[Evseev, Serguei]

Hi,

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'

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?

Thanks,
Serguei

The information contained in this electronic mail transmission 
may be privileged and confidential, and therefore, protected 
from disclosure. If you have received this communication in 
error, please notify us immediately by replying to this 
message and deleting it from your computer without copying 
or disclosing it.

[U-Boot] Kernel patch for CONFIG_LOGBUFFER

[Detlev Zundel]

Hi Serguei,

> 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.

Cheers
  Detlev

[1] http://www.mail-archive.com/linux-embedded at vger.kernel.org/msg01945.html

-- 
Computers are useless. They can only give you answers.
             -- Pablo Picasso
--
DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at denx.de

[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@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

The information contained in this electronic mail transmission 
may be privileged and confidential, and therefore, protected 
from disclosure. If you have received this communication in 
error, please notify us immediately by replying to this 
message and deleting it from your computer without copying 
or disclosing it.