On Mon, Jun 30, 2014 at 12:30:51PM +0100, Daniel Thompson wrote:

This patchset removes some single-platform compatibility tricks related
to DEBUG_LL and, as a result, allows multi_v7_defconfig derived builds
to enable DEBUG_LL. Currently the user selected kbuild setting is
ignored and the PL01X's DEBUG_LL stub is silently selected instead. This
is a pain if your hardware doesn't have this cell, not least because it
takes a little time to figure out that kbuild built the wrong code.

I don't think this is quite right, because I'm now seeing randconfig
finding build errors with this.  We can end up with this configuration:

CONFIG_DEBUG_LL=y
CONFIG_DEBUG_LL_UART_NONE=y
# CONFIG_DEBUG_ICEDCC is not set
# CONFIG_DEBUG_SEMIHOSTING is not set
# CONFIG_DEBUG_LL_UART_8250 is not set
# CONFIG_DEBUG_LL_UART_PL01X is not set
CONFIG_DEBUG_LL_INCLUDE="mach/debug-macro.S"
# CONFIG_DEBUG_UART_8250 is not set

which results in:

arch/arm/kernel/debug.S:24:33: fatal error: mach/debug-macro.S: No such file or directory
make[2]: *** [arch/arm/kernel/debug.o] Error 1
arch/arm/kernel/head.S:27:33: fatal error: mach/debug-macro.S: No such file or directory
make[2]: *** [arch/arm/kernel/head.o] Error 1

Full config file:
http://www.arm.linux.org.uk/developer/build/file.php?lid=11023

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