linux/Documentation/printk-formats.txt
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   1If variable is of Type,         use printk format specifier:
   2---------------------------------------------------------
   3                int                     %d or %x
   4                unsigned int            %u or %x
   5                long                    %ld or %lx
   6                unsigned long           %lu or %lx
   7                long long               %lld or %llx
   8                unsigned long long      %llu or %llx
   9                size_t                  %zu or %zx
  10                ssize_t                 %zd or %zx
  11
  12Raw pointer value SHOULD be printed with %p. The kernel supports
  13the following extended format specifiers for pointer types:
  14
  15Symbols/Function Pointers:
  16
  17        %pF     versatile_init+0x0/0x110
  18        %pf     versatile_init
  19        %pS     versatile_init+0x0/0x110
  20        %ps     versatile_init
  21        %pB     prev_fn_of_versatile_init+0x88/0x88
  22
  23        For printing symbols and function pointers. The 'S' and 's' specifiers
  24        result in the symbol name with ('S') or without ('s') offsets. Where
  25        this is used on a kernel without KALLSYMS - the symbol address is
  26        printed instead.
  27
  28        The 'B' specifier results in the symbol name with offsets and should be
  29        used when printing stack backtraces. The specifier takes into
  30        consideration the effect of compiler optimisations which may occur
  31        when tail-call's are used and marked with the noreturn GCC attribute.
  32
  33        On ia64, ppc64 and parisc64 architectures function pointers are
  34        actually function descriptors which must first be resolved. The 'F' and
  35        'f' specifiers perform this resolution and then provide the same
  36        functionality as the 'S' and 's' specifiers.
  37
  38Kernel Pointers:
  39
  40        %pK     0x01234567 or 0x0123456789abcdef
  41
  42        For printing kernel pointers which should be hidden from unprivileged
  43        users. The behaviour of %pK depends on the kptr_restrict sysctl - see
  44        Documentation/sysctl/kernel.txt for more details.
  45
  46Struct Resources:
  47
  48        %pr     [mem 0x60000000-0x6fffffff flags 0x2200] or
  49                [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
  50        %pR     [mem 0x60000000-0x6fffffff pref] or
  51                [mem 0x0000000060000000-0x000000006fffffff pref]
  52
  53        For printing struct resources. The 'R' and 'r' specifiers result in a
  54        printed resource with ('R') or without ('r') a decoded flags member.
  55
  56Raw buffer as a hex string:
  57        %*ph    00 01 02  ...  3f
  58        %*phC   00:01:02: ... :3f
  59        %*phD   00-01-02- ... -3f
  60        %*phN   000102 ... 3f
  61
  62        For printing a small buffers (up to 64 bytes long) as a hex string with
  63        certain separator. For the larger buffers consider to use
  64        print_hex_dump().
  65
  66MAC/FDDI addresses:
  67
  68        %pM     00:01:02:03:04:05
  69        %pMR    05:04:03:02:01:00
  70        %pMF    00-01-02-03-04-05
  71        %pm     000102030405
  72
  73        For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
  74        specifiers result in a printed address with ('M') or without ('m') byte
  75        separators. The default byte separator is the colon (':').
  76
  77        Where FDDI addresses are concerned the 'F' specifier can be used after
  78        the 'M' specifier to use dash ('-') separators instead of the default
  79        separator.
  80
  81        For Bluetooth addresses the 'R' specifier shall be used after the 'M'
  82        specifier to use reversed byte order suitable for visual interpretation
  83        of Bluetooth addresses which are in the little endian order.
  84
  85IPv4 addresses:
  86
  87        %pI4    1.2.3.4
  88        %pi4    001.002.003.004
  89        %p[Ii][hnbl]
  90
  91        For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
  92        specifiers result in a printed address with ('i4') or without ('I4')
  93        leading zeros.
  94
  95        The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
  96        host, network, big or little endian order addresses respectively. Where
  97        no specifier is provided the default network/big endian order is used.
  98
  99IPv6 addresses:
 100
 101        %pI6    0001:0002:0003:0004:0005:0006:0007:0008
 102        %pi6    00010002000300040005000600070008
 103        %pI6c   1:2:3:4:5:6:7:8
 104
 105        For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
 106        specifiers result in a printed address with ('I6') or without ('i6')
 107        colon-separators. Leading zeros are always used.
 108
 109        The additional 'c' specifier can be used with the 'I' specifier to
 110        print a compressed IPv6 address as described by
 111        http://tools.ietf.org/html/rfc5952
 112
 113UUID/GUID addresses:
 114
 115        %pUb    00010203-0405-0607-0809-0a0b0c0d0e0f
 116        %pUB    00010203-0405-0607-0809-0A0B0C0D0E0F
 117        %pUl    03020100-0504-0706-0809-0a0b0c0e0e0f
 118        %pUL    03020100-0504-0706-0809-0A0B0C0E0E0F
 119
 120        For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
 121        'b' and 'B' specifiers are used to specify a little endian order in
 122        lower ('l') or upper case ('L') hex characters - and big endian order
 123        in lower ('b') or upper case ('B') hex characters.
 124
 125        Where no additional specifiers are used the default little endian
 126        order with lower case hex characters will be printed.
 127
 128struct va_format:
 129
 130        %pV
 131
 132        For printing struct va_format structures. These contain a format string
 133        and va_list as follows:
 134
 135        struct va_format {
 136                const char *fmt;
 137                va_list *va;
 138        };
 139
 140        Do not use this feature without some mechanism to verify the
 141        correctness of the format string and va_list arguments.
 142
 143u64 SHOULD be printed with %llu/%llx, (unsigned long long):
 144
 145        printk("%llu", (unsigned long long)u64_var);
 146
 147s64 SHOULD be printed with %lld/%llx, (long long):
 148
 149        printk("%lld", (long long)s64_var);
 150
 151If <type> is dependent on a config option for its size (e.g., sector_t,
 152blkcnt_t, phys_addr_t, resource_size_t) or is architecture-dependent
 153for its size (e.g., tcflag_t), use a format specifier of its largest
 154possible type and explicitly cast to it.  Example:
 155
 156        printk("test: sector number/total blocks: %llu/%llu\n",
 157                (unsigned long long)sector, (unsigned long long)blockcount);
 158
 159Reminder: sizeof() result is of type size_t.
 160
 161Thank you for your cooperation and attention.
 162
 163
 164By Randy Dunlap <rdunlap@xenotime.net> and
 165Andrew Murray <amurray@mpc-data.co.uk>
 166
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