[转]printk usage

原文地址：http://elinux.org/Debugging_by_printing#Usage 

If variable is of Type,		use printk format specifier:

---------------------------------------------------------

		int			%d or %x

		unsigned int		%u or %x

		long			%ld or %lx

		unsigned long		%lu or %lx

		long long		%lld or %llx

		unsigned long long	%llu or %llx

		size_t			%zu or %zx

		ssize_t			%zd or %zx

Raw pointer value SHOULD be printed with %p. The kernel supports

the following extended format specifiers for pointer types:
Symbols/Function Pointers:
%pF	versatile_init+0x0/0x110

	%pf	versatile_init

	%pS	versatile_init+0x0/0x110

	%pSR	versatile_init+0x9/0x110

		(with __builtin_extract_return_addr() translation)

	%ps	versatile_init

	%pB	prev_fn_of_versatile_init+0x88/0x88
For printing symbols and function pointers. The ‘S‘ and ‘s‘ specifiers

	result in the symbol name with (‘S‘) or without (‘s‘) offsets. Where

	this is used on a kernel without KALLSYMS - the symbol address is

	printed instead.
The ‘B‘ specifier results in the symbol name with offsets and should be

	used when printing stack backtraces. The specifier takes into

	consideration the effect of compiler optimisations which may occur

	when tail-call‘s are used and marked with the noreturn GCC attribute.
On ia64, ppc64 and parisc64 architectures function pointers are

	actually function descriptors which must first be resolved. The ‘F‘ and

	‘f‘ specifiers perform this resolution and then provide the same

	functionality as the ‘S‘ and ‘s‘ specifiers.
Kernel Pointers:
%pK	0x01234567 or 0x0123456789abcdef
For printing kernel pointers which should be hidden from unprivileged

	users. The behaviour of %pK depends on the kptr_restrict sysctl - see

	Documentation/sysctl/kernel.txt for more details.
Struct Resources:
%pr	[mem 0x60000000-0x6fffffff flags 0x2200] or

		[mem 0x0000000060000000-0x000000006fffffff flags 0x2200]

	%pR	[mem 0x60000000-0x6fffffff pref] or

		[mem 0x0000000060000000-0x000000006fffffff pref]
For printing struct resources. The ‘R‘ and ‘r‘ specifiers result in a

	printed resource with (‘R‘) or without (‘r‘) a decoded flags member.
Physical addresses:
%pa	0x01234567 or 0x0123456789abcdef
For printing a phys_addr_t type (and its derivatives, such as

	resource_size_t) which can vary based on build options, regardless of

	the width of the CPU data path. Passed by reference.
Raw buffer as a hex string:

	%*ph	00 01 02  ...  3f

	%*phC	00:01:02: ... :3f

	%*phD	00-01-02- ... -3f

	%*phN	000102 ... 3f
For printing a small buffers (up to 64 bytes long) as a hex string with

	certain separator. For the larger buffers consider to use

	print_hex_dump().
MAC/FDDI addresses:
%pM	00:01:02:03:04:05

	%pMR	05:04:03:02:01:00

	%pMF	00-01-02-03-04-05

	%pm	000102030405

	%pmR	050403020100
For printing 6-byte MAC/FDDI addresses in hex notation. The ‘M‘ and ‘m‘

	specifiers result in a printed address with (‘M‘) or without (‘m‘) byte

	separators. The default byte separator is the colon (‘:‘).
Where FDDI addresses are concerned the ‘F‘ specifier can be used after

	the ‘M‘ specifier to use dash (‘-‘) separators instead of the default

	separator.
For Bluetooth addresses the ‘R‘ specifier shall be used after the ‘M‘

	specifier to use reversed byte order suitable for visual interpretation

	of Bluetooth addresses which are in the little endian order.
IPv4 addresses:
%pI4	1.2.3.4

	%pi4	001.002.003.004

	%p[Ii][hnbl]
For printing IPv4 dot-separated decimal addresses. The ‘I4‘ and ‘i4‘

	specifiers result in a printed address with (‘i4‘) or without (‘I4‘)

	leading zeros.
The additional ‘h‘, ‘n‘, ‘b‘, and ‘l‘ specifiers are used to specify

	host, network, big or little endian order addresses respectively. Where

	no specifier is provided the default network/big endian order is used.
IPv6 addresses:
%pI6	0001:0002:0003:0004:0005:0006:0007:0008

	%pi6	00010002000300040005000600070008

	%pI6c	1:2:3:4:5:6:7:8
For printing IPv6 network-order 16-bit hex addresses. The ‘I6‘ and ‘i6‘

	specifiers result in a printed address with (‘I6‘) or without (‘i6‘)

	colon-separators. Leading zeros are always used.
The additional ‘c‘ specifier can be used with the ‘I‘ specifier to

	print a compressed IPv6 address as described by

	http://tools.ietf.org/html/rfc5952
UUID/GUID addresses:
%pUb	00010203-0405-0607-0809-0a0b0c0d0e0f

	%pUB	00010203-0405-0607-0809-0A0B0C0D0E0F

	%pUl	03020100-0504-0706-0809-0a0b0c0e0e0f

	%pUL	03020100-0504-0706-0809-0A0B0C0E0E0F
For printing 16-byte UUID/GUIDs addresses. The additional ‘l‘, ‘L‘,

	‘b‘ and ‘B‘ specifiers are used to specify a little endian order in

	lower (‘l‘) or upper case (‘L‘) hex characters - and big endian order

	in lower (‘b‘) or upper case (‘B‘) hex characters.
Where no additional specifiers are used the default little endian

	order with lower case hex characters will be printed.
struct va_format:
%pV
For printing struct va_format structures. These contain a format string

	and va_list as follows:
struct va_format {

		const char *fmt;

		va_list *va;

	};
Do not use this feature without some mechanism to verify the

	correctness of the format string and va_list arguments.
u64 SHOULD be printed with %llu/%llx, (unsigned long long):
printk("%llu", (unsigned long long)u64_var);
s64 SHOULD be printed with %lld/%llx, (long long):
printk("%lld", (long long)s64_var);
If <type> is dependent on a config option for its size (e.g., sector_t,

blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a

format specifier of its largest possible type and explicitly cast to it.

Example:
printk("test: sector number/total blocks: %llu/%llu\n",

		(unsigned long long)sector, (unsigned long long)blockcount);
Reminder: sizeof() result is of type size_t.
Thank you for your cooperation and attention.

Reference:

http://elinux.org/Kernel_Debugging_Tips#Using_a_kernel_debugger 

http://blog.csdn.net/yihui8/article/details/6736679 

By Randy Dunlap <[email protected]> and

Andrew Murray <[email protected]> 

[转]printk usage,布布扣,bubuko.com