linux-kernel - Building sh4 without CONFIG

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Date:	Sun, 11 May 2014 18:53:21 -0500
From:	Rob Landley <rob@...dley.net>
To:	linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Building sh4 without CONFIG_EXPERT.

I got sh4 to work under QEMU years ago as part of my aboriginal linux
project, which builds the smallest Linux system capable of rebuilding
itself natively from source code. (You can download and run the system
images from http://landley.net/aboriginal/bin if you're curious.)

One of the goals of Aboriginal is to make different architectures behave
the same way, and one of the ways I do that is by having a basic kernel
miniconfig file defining the config symbols common across platforms:

  http://landley.net/hg/aboriginal/file/1651/sources/baseconfig-linux

And then append target-specific chunks, ala the LINUX_CONFIG sections
from each of:

  http://landley.net/hg/aboriginal/file/1651/sources/targets

The problem is, the sh4 target's target-specific chunk is an INSANE 45
config symbols (armv5l needs 15 symbols, powerpc needs 16, i686 needs 7,
mips needs 6...) and the reason for the verbosity is that sh4 forces on
CONFIG_EXPERT.

As far as I can tell, the only reason sh4 is forcing on CONFIG_EXPERT is
to get CONFIG_PATA_PLATFORM. The patch to make sh4 _not_ force on
CONFIG_EXPERT is just:

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 834b67c..7d0d44d 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -1,7 +1,7 @@
 config SUPERH
 	def_bool y
 	select ARCH_MIGHT_HAVE_PC_PARPORT
-	select EXPERT
+	select HAVE_PATA_PLATFORM
 	select CLKDEV_LOOKUP
 	select HAVE_IDE if HAS_IOPORT_MAP
 	select HAVE_MEMBLOCK

Which swaps EXPERT for HAVE_PATA_PLATFORM, so I can still provide a hard
drive qemu can see as /dev/sda. The result builds, boots, and works for
me in very basic smoke testing, and lets me get my sh4-specific config
symbol set down to 27 symbols.

(P.S. I have no idea why hitting ctrl-C kills the _emulator_ rather than
passing it along to the emulated system. The other qemu targets don't do
that...)

Rob

P.S. I'm using linux 3.14, qemu 2.0, and the sh4 cross compiler
toolchain from the URL at the top of the post. I can be more explicit if
you care...
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