f0d1b0b30d
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>
215 lines
5.9 KiB
Plaintext
215 lines
5.9 KiB
Plaintext
#
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# For a description of the syntax of this configuration file,
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# see Documentation/kbuild/config-language.txt.
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#
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mainmenu "uClinux/h8300 (w/o MMU) Kernel Configuration"
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config H8300
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bool
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default y
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config MMU
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bool
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default n
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config SWAP
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bool
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default n
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config FPU
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bool
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default n
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config RWSEM_GENERIC_SPINLOCK
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bool
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default y
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config RWSEM_XCHGADD_ALGORITHM
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bool
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default n
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config ARCH_HAS_ILOG2_U32
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bool
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default n
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config ARCH_HAS_ILOG2_U64
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bool
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default n
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config GENERIC_FIND_NEXT_BIT
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bool
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default y
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config GENERIC_HWEIGHT
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bool
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default y
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config GENERIC_CALIBRATE_DELAY
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bool
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default y
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config TIME_LOW_RES
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bool
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default y
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config ISA
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bool
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default y
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config PCI
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bool
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default n
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source "init/Kconfig"
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source "arch/h8300/Kconfig.cpu"
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menu "Executable file formats"
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source "fs/Kconfig.binfmt"
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endmenu
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source "net/Kconfig"
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source "drivers/base/Kconfig"
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source "drivers/mtd/Kconfig"
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source "drivers/block/Kconfig"
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source "drivers/ide/Kconfig"
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source "arch/h8300/Kconfig.ide"
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source "drivers/net/Kconfig"
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#
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# input - input/joystick depends on it. As does USB.
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#
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source "drivers/input/Kconfig"
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menu "Character devices"
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config VT
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bool "Virtual terminal"
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---help---
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If you say Y here, you will get support for terminal devices with
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display and keyboard devices. These are called "virtual" because you
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can run several virtual terminals (also called virtual consoles) on
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one physical terminal. This is rather useful, for example one
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virtual terminal can collect system messages and warnings, another
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one can be used for a text-mode user session, and a third could run
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an X session, all in parallel. Switching between virtual terminals
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is done with certain key combinations, usually Alt-<function key>.
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The setterm command ("man setterm") can be used to change the
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properties (such as colors or beeping) of a virtual terminal. The
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man page console_codes(4) ("man console_codes") contains the special
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character sequences that can be used to change those properties
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directly. The fonts used on virtual terminals can be changed with
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the setfont ("man setfont") command and the key bindings are defined
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with the loadkeys ("man loadkeys") command.
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You need at least one virtual terminal device in order to make use
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of your keyboard and monitor. Therefore, only people configuring an
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embedded system would want to say N here in order to save some
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memory; the only way to log into such a system is then via a serial
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or network connection.
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If unsure, say Y, or else you won't be able to do much with your new
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shiny Linux system :-)
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config VT_CONSOLE
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bool "Support for console on virtual terminal"
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depends on VT
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---help---
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The system console is the device which receives all kernel messages
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and warnings and which allows logins in single user mode. If you
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answer Y here, a virtual terminal (the device used to interact with
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a physical terminal) can be used as system console. This is the most
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common mode of operations, so you should say Y here unless you want
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the kernel messages be output only to a serial port (in which case
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you should say Y to "Console on serial port", below).
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If you do say Y here, by default the currently visible virtual
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terminal (/dev/tty0) will be used as system console. You can change
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that with a kernel command line option such as "console=tty3" which
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would use the third virtual terminal as system console. (Try "man
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bootparam" or see the documentation of your boot loader (lilo or
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loadlin) about how to pass options to the kernel at boot time.)
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If unsure, say Y.
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config HW_CONSOLE
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bool
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depends on VT && !S390 && !UM
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default y
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comment "Unix98 PTY support"
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config UNIX98_PTYS
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bool "Unix98 PTY support"
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---help---
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A pseudo terminal (PTY) is a software device consisting of two
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halves: a master and a slave. The slave device behaves identical to
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a physical terminal; the master device is used by a process to
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read data from and write data to the slave, thereby emulating a
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terminal. Typical programs for the master side are telnet servers
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and xterms.
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Linux has traditionally used the BSD-like names /dev/ptyxx for
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masters and /dev/ttyxx for slaves of pseudo terminals. This scheme
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has a number of problems. The GNU C library glibc 2.1 and later,
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however, supports the Unix98 naming standard: in order to acquire a
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pseudo terminal, a process opens /dev/ptmx; the number of the pseudo
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terminal is then made available to the process and the pseudo
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terminal slave can be accessed as /dev/pts/<number>. What was
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traditionally /dev/ttyp2 will then be /dev/pts/2, for example.
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The entries in /dev/pts/ are created on the fly by a virtual
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file system; therefore, if you say Y here you should say Y to
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"/dev/pts file system for Unix98 PTYs" as well.
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If you want to say Y here, you need to have the C library glibc 2.1
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or later (equal to libc-6.1, check with "ls -l /lib/libc.so.*").
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Read the instructions in <file:Documentation/Changes> pertaining to
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pseudo terminals. It's safe to say N.
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config UNIX98_PTY_COUNT
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int "Maximum number of Unix98 PTYs in use (0-2048)"
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depends on UNIX98_PTYS
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default "256"
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help
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The maximum number of Unix98 PTYs that can be used at any one time.
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The default is 256, and should be enough for desktop systems. Server
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machines which support incoming telnet/rlogin/ssh connections and/or
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serve several X terminals may want to increase this: every incoming
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connection and every xterm uses up one PTY.
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When not in use, each additional set of 256 PTYs occupy
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approximately 8 KB of kernel memory on 32-bit architectures.
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source "drivers/char/pcmcia/Kconfig"
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source "drivers/serial/Kconfig"
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source "drivers/i2c/Kconfig"
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source "drivers/hwmon/Kconfig"
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source "drivers/usb/Kconfig"
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endmenu
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source "fs/Kconfig"
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source "arch/h8300/Kconfig.debug"
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source "security/Kconfig"
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source "crypto/Kconfig"
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source "lib/Kconfig"
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