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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>
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| lib | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| 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.