[PATCH v8 0/3] x86/earlyprintk: setup serial earlyprintk as early as possible

[Alexander Kuleshov]

The early_printk function is usable only after the setup_early_printk will
be executed. We pass 'earlyprintk' through the kernel command line. So, it
means that earlyprintk will be usable only after the 'parse_early_param'
will be executed. We have usable earlyprintk only during early boot, kernel
decompression and after call of the 'parse_early_param'. This patchset makes
serial earlyprintk usable before the call of the 'parse_early_param'.

Patchset was tested for both x86 and x86_64 architectures with the qemu.

These patchset provides following changes:

1. Move handling of the builtin command line to the separate function
from the setup_arch. Now we can call it from the arch/x86/kernel/head{32,64}.c,
and find 'earlyprintk' kernel command line paramter there.

2. Provide setup_serial_console function to setup serial earlyprintk in the
arch/x86/kernel/head{32,64}.c

v8:

* Fixed warning with the definition of the setup_early_serial_console
in the arch/x86/include/asm/setup.h

v7:

* Move setup_early_serial_console to the the arch/x86/include/setup.h
* Add ifdefs to prevent setup_serial_console if CONFIG_EARLY_PRINTK
is not set.

v6:

* Style fixes.
* Call of the suetp_builtin_cmdline moved to the separate patch.

v5:

* Call setup_builtin_cmdline instead of setup_cmdline

v4:

* Move setup_early_serial_console from the include/linux/printk.h
to the arch/x86/include/asm/serial.h, because this function is only
for x86 now.

v3:

* Call setup_cmdline before setup_early_printk;
* setup_early_printk call wrapped with the setup_early_serial_console which
checks that 'serial' given to the earlyprintk command line option. This
prevents call of the setup_early_printk with the given pciserial/dbgp/efi,
because they are using early_ioremap.

v2:

* Comment added before the setup_early_printk call;
* Added information about testing to the commit message.

Alexander Kuleshov (3):
  x86/setup: introduce setup_bultin_cmdline
  x86/setup: handle builtin command line as early as possible
  x86/earlyprintk: setup earlyprintk as early as possible

 arch/x86/include/asm/setup.h   |  8 ++++++++
 arch/x86/kernel/early_printk.c | 24 ++++++++++++++++++++++++
 arch/x86/kernel/head32.c       |  7 +++++++
 arch/x86/kernel/head64.c       |  7 +++++++
 arch/x86/kernel/setup.c        | 33 ++++++++++++++++++---------------
 5 files changed, 64 insertions(+), 15 deletions(-)

--
2.4.0.350.g9532ead

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