WAIT_ON_BIT_LOCK(9) Driver Basics WAIT_ON_BIT_LOCK(9)NAME
wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it
SYNOPSIS
int wait_on_bit_lock(void * word, int bit, int (*action) (void *), unsigned mode);
ARGUMENTS
word
the word being waited on, a kernel virtual address
bit
the bit of the word being waited on
action
the function used to sleep, which may take special actions
mode
the task state to sleep in
DESCRIPTION
There is a standard hashed waitqueue table for generic use. This is the part of the hashtable's accessor API that waits on a bit when one
intends to set it, for instance, trying to lock bitflags. For instance, if one were to have waiters trying to set bitflag and waiting for
it to clear before setting it, one would call wait_on_bit in threads waiting to be able to set the bit. One uses wait_on_bit_lock where one
is waiting for the bit to clear with the intention of setting it, and when done, clearing it.
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 WAIT_ON_BIT_LOCK(9)
Check Out this Related Man Page
swap_lw_bytes(9r)swap_lw_bytes(9r)NAME
swap_lw_bytes, swap_word_bytes, swap_words - General: Perform byte-swapping operations
SYNOPSIS
unsigned int swap_lw_bytes(
unsigned int buffer ); unsigned int swap_word_bytes(
unsigned int buffer ); unsigned int swap_words(
unsigned int buffer );
ARGUMENTS
Specifies a 32-bit (4 bytes) quantity.
DESCRIPTION
The swap_lw_bytes interface performs a longword byte swap. The swap_word_bytes interface performs a short word byte swap. The swap_words
interface performs a word byte swap. Many computer vendors support devices that use a big endian model of byte ordering. Because Digital
devices support the little endian model of byte ordering, there is a need for these byte-swapping interfaces. In addition, some buses (for
example, the VMEbus) can have specific or implied byte ordering that may require the use of these interfaces.
Given that a longword is equal to 4 bytes; a short word is equal to 2 bytes; and 1 byte is equal to 8 bits, these interfaces swap bytes as
follows: The swap_lw_bytes interface takes the 32-bit quantity specified by the buffer argument and swaps all 4 bytes. The swap_word_bytes
interface takes the 32-bit quantity specified by the buffer argument and swaps the individual bytes that make up each word of the 32-bit
quantity. The swap_words interface takes the 32-bit quantity specified by the buffer argument and swaps the two 16-bit words.
The following illustration compares the byte swapping performed by these interfaces.
31 0
+---+---+---+---+ Starting value: | a | b | c | d |
+---+---+---+---+
Long word byte swap
(swap_lw_bytes)
31 0
+---+---+---+---+ Ending value: | d | c | b | a |
+-------+---+---+
Short word byte swap
(swap_word_bytes)
31 0
+---+---+---+---+ Ending value: | b | a | d | c |
+---+---+---+---+
31 0
+---+---+---+---+ Starting value: | ab | cd |
+---+---+---+---+
Word byte swap
(swap_words)
31 0
+---+---+---+---+ Ending value: | cd | ab |
+---+---+---+---+
RETURN VALUES
Upon successful completion, these interfaces return the swapped bytes.
swap_lw_bytes(9r)
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