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
  		s32			%d or %x
  		u32			%u or %x
  		s64			%lld or %llx
  		u64			%llu or %llx
  
  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
  ",
  		(unsigned long long)sector, (unsigned long long)blockcount);
  
  Reminder: sizeof() result is of type size_t.
  
  The kernel's printf does not support %n. For obvious reasons, floating
  point formats (%e, %f, %g, %a) are also not recognized. Use of any
  unsupported specifier or length qualifier results in a WARN and early
  return from vsnprintf.
  
  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.
  	Passed by reference.
  
  Physical addresses types phys_addr_t:
  
  	%pa[p]	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.
  
  DMA addresses types dma_addr_t:
  
  	%pad	0x01234567 or 0x0123456789abcdef
  
  	For printing a dma_addr_t type which can vary based on build options,
  	regardless of the width of the CPU data path. Passed by reference.
  
  Raw buffer as an escaped string:
  
  	%*pE[achnops]
  
  	For printing raw buffer as an escaped string. For the following buffer
  
  		1b 62 20 5c 43 07 22 90 0d 5d
  
  	few examples show how the conversion would be done (the result string
  	without surrounding quotes):
  
  		%*pE		"\eb \C\a"\220\r]"
  		%*pEhp		"\x1bb \C\x07"\x90\x0d]"
  		%*pEa		"\e\142\040\\\103\a\042\220\r\135"
  
  	The conversion rules are applied according to an optional combination
  	of flags (see string_escape_mem() kernel documentation for the
  	details):
  		a - ESCAPE_ANY
  		c - ESCAPE_SPECIAL
  		h - ESCAPE_HEX
  		n - ESCAPE_NULL
  		o - ESCAPE_OCTAL
  		p - ESCAPE_NP
  		s - ESCAPE_SPACE
  	By default ESCAPE_ANY_NP is used.
  
  	ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
  	printing SSIDs.
  
  	If field width is omitted the 1 byte only will be escaped.
  
  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.
  
  	Passed by reference.
  
  IPv4 addresses:
  
  	%pI4	1.2.3.4
  	%pi4	001.002.003.004
  	%p[Ii]4[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.
  
  	Passed by reference.
  
  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
  
  	Passed by reference.
  
  IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
  
  	%pIS	1.2.3.4		or 0001:0002:0003:0004:0005:0006:0007:0008
  	%piS	001.002.003.004	or 00010002000300040005000600070008
  	%pISc	1.2.3.4		or 1:2:3:4:5:6:7:8
  	%pISpc	1.2.3.4:12345	or [1:2:3:4:5:6:7:8]:12345
  	%p[Ii]S[pfschnbl]
  
  	For printing an IP address without the need to distinguish whether it's
  	of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
  	specified through 'IS' or 'iS', can be passed to this format specifier.
  
  	The additional 'p', 'f', and 's' specifiers are used to specify port
  	(IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
  	flowinfo a '/' and scope a '%', each followed by the actual value.
  
  	In case of an IPv6 address the compressed IPv6 address as described by
  	http://tools.ietf.org/html/rfc5952 is being used if the additional
  	specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in
  	case of additional specifiers 'p', 'f' or 's' as suggested by
  	https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
  
  	In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l'
  	specifiers can be used as well and are ignored in case of an IPv6
  	address.
  
  	Passed by reference.
  
  	Further examples:
  
  	%pISfc		1.2.3.4		or [1:2:3:4:5:6:7:8]/123456789
  	%pISsc		1.2.3.4		or [1:2:3:4:5:6:7:8]%1234567890
  	%pISpfc		1.2.3.4:12345	or [1:2:3:4:5:6:7:8]:12345/123456789
  
  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 big endian
  	order with lower case hex characters will be printed.
  
  	Passed by reference.
  
  dentry names:
  
  	%pd{,2,3,4}
  	%pD{,2,3,4}
  
  	For printing dentry name; if we race with d_move(), the name might be
  	a mix of old and new ones, but it won't oops.  %pd dentry is a safer
  	equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
  	n last components.  %pD does the same thing for struct file.
  
  	Passed by reference.
  
  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;
  	};
  
  	Implements a "recursive vsnprintf".
  
  	Do not use this feature without some mechanism to verify the
  	correctness of the format string and va_list arguments.
  
  	Passed by reference.
  
  struct clk:
  
  	%pC	pll1
  	%pCn	pll1
  	%pCr	1560000000
  
  	For printing struct clk structures. '%pC' and '%pCn' print the name
  	(Common Clock Framework) or address (legacy clock framework) of the
  	structure; '%pCr' prints the current clock rate.
  
  	Passed by reference.
  
  bitmap and its derivatives such as cpumask and nodemask:
  
  	%*pb	0779
  	%*pbl	0,3-6,8-10
  
  	For printing bitmap and its derivatives such as cpumask and nodemask,
  	%*pb output the bitmap with field width as the number of bits and %*pbl
  	output the bitmap as range list with field width as the number of bits.
  
  	Passed by reference.
  
  Network device features:
  
  	%pNF	0x000000000000c000
  
  	For printing netdev_features_t.
  
  	Passed by reference.
  
  Command from struct task_struct
  
  	%pT	ls
  
  	For printing executable name excluding path from struct
  	task_struct.
  
  	Passed by reference.
  
  If you add other %p extensions, please extend lib/test_printf.c with
  one or more test cases, if at all feasible.
  
  
  Thank you for your cooperation and attention.
  
  
  By Randy Dunlap <rdunlap@infradead.org> and
  Andrew Murray <amurray@mpc-data.co.uk>