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David Howells f0d1b0b30d [PATCH] LOG2: Implement a general integer log2 facility in the kernel 
This facility provides three entry points:

	ilog2()		Log base 2 of unsigned long
	ilog2_u32()	Log base 2 of u32
	ilog2_u64()	Log base 2 of u64

These facilities can either be used inside functions on dynamic data:

	int do_something(long q)
	{
		...;
		y = ilog2(x)
		...;
	}

Or can be used to statically initialise global variables with constant values:

	unsigned n = ilog2(27);

When performing static initialisation, the compiler will report "error:
initializer element is not constant" if asked to take a log of zero or of
something not reducible to a constant.  They treat negative numbers as
unsigned.

When not dealing with a constant, they fall back to using fls() which permits
them to use arch-specific log calculation instructions - such as BSR on
x86/x86_64 or SCAN on FRV - if available.

[akpm@osdl.org: MMC fix]
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Howells <dhowells@redhat.com>
Cc: Wojtek Kaniewski <wojtekka@toxygen.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:28:51 -08:00
..
configs
kernel
lib
Kconfig
Kconfig.debug
Makefile
README

README 

This port to the NEC V850E processor supports the following platforms:

   "sim"
	The gdb v850e simulator (CONFIG_V850E_SIM).

   "rte-ma1-cb"
	The Midas labs RTE-V850E/MA1-CB and RTE-V850E/NB85E-CB evaluation
	boards (CONFIG_RTE_CB_MA1 and CONFIG_RTE_CB_NB85E).  This support
	has only been tested when running with the Multi-debugger monitor
	ROM (for the Green Hills Multi debugger).  The optional NEC
	Solution Gear RTE-MOTHER-A motherboard is also supported, which
	allows PCI boards to be used (CONFIG_RTE_MB_A_PCI).

   "rte-me2-cb"
	The Midas labs RTE-V850E/ME2-CB evaluation board (CONFIG_RTE_CB_ME2).
     	This has only been tested using a kernel downloaded via an ICE
     	connection using the Multi debugger.  Support for the RTE-MOTHER-A is
     	present, but hasn't been tested (unlike the other Midas labs cpu
     	boards, the RTE-V850E/ME2-CB includes an ethernet adaptor).

   "as85ep1"
	The NEC AS85EP1 V850E evaluation chip/board (CONFIG_V850E_AS85EP1).

   "anna"
	The NEC `Anna' (board/chip) implementation of the V850E2 processor
	(CONFIG_V850E2_ANNA).

   "sim85e2c", "sim85e2s"
   	The sim85e2c and sim85e2s simulators, which are verilog simulations
	of the V850E2 NA85E2C/NA85E2S cpu cores (CONFIG_V850E2_SIM85E2C and
	CONFIG_V850E2_SIM85E2S).

   "fpga85e2c"
	A FPGA implementation of the V850E2 NA85E2C cpu core
	(CONFIG_V850E2_FPGA85E2C).

To get a default kernel configuration for a particular platform, you can
use a <platform>_defconfig make target (e.g., "make rte-me2-cb_defconfig");
to see which default configurations are possible, look in the directory
"arch/v850/configs".

Porting to anything with a V850E/MA1 or MA2 processor should be simple.
See the file <asm-v850/machdep.h> and the files it includes for an example of
how to add platform/chip-specific support.