-If variable is of Type, use printk format specifier:
----------------------------------------------------------
+=========================================
+How to get printk format specifiers right
+=========================================
+
+:Author: Randy Dunlap <rdunlap@infradead.org>
+:Author: Andrew Murray <amurray@mpc-data.co.uk>
+
+
+Integer types
+=============
+
+::
+
+ If variable is of Type, use printk format specifier:
+ ------------------------------------------------------------
int %d or %x
unsigned int %u or %x
long %ld or %lx
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:
+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.
+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
+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:
+Symbols/Function Pointers
+=========================
+
+::
%pF versatile_init+0x0/0x110
%pf versatile_init
%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.
+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.
- 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.
- 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
+===============
-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.
+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
+================
-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.
+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``
+========================================
-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.
+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:
+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.
+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
+===============================
-Raw buffer as an escaped string:
+::
%*pE[achnops]
- For printing raw buffer as an escaped string. For the following buffer
+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):
+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.
+The conversion rules are applied according to an optional combination
+of flags (see :c:func:`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
- ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
- printing SSIDs.
+By default ESCAPE_ANY_NP is used.
- If field width is omitted the 1 byte only will be escaped.
+ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
+printing SSIDs.
-Raw buffer as a hex string:
+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().
+For printing a small buffers (up to 64 bytes long) as a hex string with
+certain separator. For the larger buffers consider to use
+:c:func:`print_hex_dump`.
+
+MAC/FDDI addresses
+==================
-MAC/FDDI addresses:
+::
%pM 00:01:02:03:04:05
%pMR 05:04:03:02:01:00
%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 (':').
+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.
+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.
+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.
+Passed by reference.
+
+IPv4 addresses
+==============
-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.
+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.
+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.
+Passed by reference.
-IPv6 addresses:
+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.
+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
+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.
+Passed by reference.
-IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
+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
%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.
+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.
+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 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.
+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.
+Passed by reference.
- Further examples:
+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:
+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.
+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.
+Where no additional specifiers are used the default big endian
+order with lower case hex characters will be printed.
- Passed by reference.
+Passed by reference.
+
+dentry names
+============
-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.
+For printing dentry name; if we race with :c:func:`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.
+Passed by reference.
-block_device names:
+block_device names
+==================
+
+::
%pg sda, sda1 or loop0p1
- For printing name of block_device pointers.
+For printing name of block_device pointers.
+
+struct va_format
+================
-struct va_format:
+::
%pV
- For printing struct va_format structures. These contain a format string
- and va_list as follows:
+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".
+Implements a "recursive vsnprintf".
- Do not use this feature without some mechanism to verify the
- correctness of the format string and va_list arguments.
+Do not use this feature without some mechanism to verify the
+correctness of the format string and va_list arguments.
- Passed by reference.
+Passed by reference.
+
+kobjects
+========
+
+::
-kobjects:
%pO
Base specifier for kobject based structs. Must be followed with
Passed by reference.
-struct clk:
+
+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.
+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.
+Passed by reference.
-bitmap and its derivatives such as cpumask and nodemask:
+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.
+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.
+Passed by reference.
+
+Flags bitfields such as page flags, gfp_flags
+=============================================
-Flags bitfields such as page flags, gfp_flags:
+::
%pGp referenced|uptodate|lru|active|private
%pGg GFP_USER|GFP_DMA32|GFP_NOWARN
%pGv read|exec|mayread|maywrite|mayexec|denywrite
- For printing flags bitfields as a collection of symbolic constants that
- would construct the value. The type of flags is given by the third
- character. Currently supported are [p]age flags, [v]ma_flags (both
- expect unsigned long *) and [g]fp_flags (expects gfp_t *). The flag
- names and print order depends on the particular type.
+For printing flags bitfields as a collection of symbolic constants that
+would construct the value. The type of flags is given by the third
+character. Currently supported are [p]age flags, [v]ma_flags (both
+expect ``unsigned long *``) and [g]fp_flags (expects ``gfp_t *``). The flag
+names and print order depends on the particular type.
- Note that this format should not be used directly in TP_printk() part
- of a tracepoint. Instead, use the show_*_flags() functions from
- <trace/events/mmflags.h>.
+Note that this format should not be used directly in :c:func:`TP_printk()` part
+of a tracepoint. Instead, use the ``show_*_flags()`` functions from
+<trace/events/mmflags.h>.
- Passed by reference.
+Passed by reference.
+
+Network device features
+=======================
-Network device features:
+::
%pNF 0x000000000000c000
- For printing netdev_features_t.
+For printing netdev_features_t.
- Passed by reference.
+Passed by reference.
-If you add other %p extensions, please extend lib/test_printf.c with
+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>
projects / karo-tx-linux.git / blobdiff