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Date: Wed, 6 Dec 2017 10:18:49 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: "Tobin C. Harding" <me@...in.cc>, Jonathan Corbet <corbet@....net>
Cc: Andrew Murray <amurray@...-data.co.uk>, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] doc: convert printk-formats.txt to rst
On 12/05/2017 05:45 PM, Tobin C. Harding wrote:
> Documentation/printk-formats.txt is a candidate for conversion to
> ReStructuredText format. Some effort has already been made to do this
> conversion even thought the suffix is currently .txt
>
> Changes required to complete conversion
>
> - Add double backticks where needed.
> - Add entry to Documentation/index.rst
> - Use flat-table instead of ASCII table.
> - Fix minor grammatical errors.
> - Capitalize headers and correctly order heading adornments.
That's a style choice and an unneeded change (referring to Capitalize headers).
> - Use 'Passed by reference' uniformly.
> - Update pointer documentation around %px specifier.
> - Fix erroneous double backticks (to commas).
> - Simplify documentation for kobject.
> - Convert lib/vsnprintf.c function docs to use kernel-docs and
> include in Documentation/printk-formats.rst
good idea.
>
> Signed-off-by: Tobin C. Harding <me@...in.cc>
> ---
>
> The last two need special reviewing please. In particular the conversion
> of kernel-docs in vsnprintf.c attempt was made to reduce documentation
> duplication with comments in the source code being simplified in order
> to be suitable for inclusion in Documentation/printk-formats.rst
>
> I used -M when formatting the patch. If you don't like the diff with
> this flag just holla.
>
> thanks,
> Tobin.
>
> Documentation/index.rst | 10 +
> .../{printk-formats.txt => printk-formats.rst} | 295 ++++++++++++---------
> lib/vsprintf.c | 160 +++++------
> 3 files changed, 235 insertions(+), 230 deletions(-)
> rename Documentation/{printk-formats.txt => printk-formats.rst} (61%)
> diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.rst
> similarity index 61%
> rename from Documentation/printk-formats.txt
> rename to Documentation/printk-formats.rst
> index aa0a776c817a..51449d213748 100644
> --- a/Documentation/printk-formats.txt
> +++ b/Documentation/printk-formats.rst
> @@ -1,6 +1,6 @@
> -=========================================
> -How to get printk format specifiers right
> -=========================================
> +=============================================
> +How to Get ``printk`` Format Specifiers Right
> +=============================================
>
> :Author: Randy Dunlap <rdunlap@...radead.org>
> :Author: Andrew Murray <amurray@...-data.co.uk>
> @@ -8,56 +8,91 @@ How to get printk format specifiers right
> Integer types
> =============
>
> -::
> +For printing integer types, we have the following format specifiers:
> +
> + .. flat-table::
> + :widths: 2 2
> +
> + * - **Type**
> + - **Specifier**
> +
> + * - ``int``
> + - ``%d`` or ``%x``
> +
> + * - ``unsigned int``
> + - ``%u`` or ``%x``
> +
> + * - ``long``
> + - ``%ld`` or ``%lx``
> +
> + * - ``unsigned long``
> + - ``%lu`` or ``%lx``
> +
> + * - ``long long``
> + - ``%lld`` or ``%llx``
>
> - 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``,
> + * - ``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\n",
> - (unsigned long long)sector, (unsigned long long)blockcount);
> + printk("test: total blocks: %llu\n", (unsigned long long)blockcount);
>
> -Reminder: ``sizeof()`` result is of type ``size_t``.
> +Reminder: ``sizeof()`` returns type ``size_t``.
>
> -The kernel's printf does not support ``%n``. For obvious reasons, floating
> +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:
> +return from ``vsnprintf()``.
>
> Pointer Types
> =============
>
> -Pointers printed without a specifier extension (i.e unadorned %p) are
> -hashed to give a unique identifier without leaking kernel addresses to user
> -space. On 64 bit machines the first 32 bits are zeroed. If you _really_
> -want the address see %px below.
> +A raw pointer value may be printed with ``%p`` which will hash the address
> +before printing. The Kernel also supports extended specifiers for printing
> +pointers of different types.
> +
> +.. kernel-doc:: lib/vsprintf.c
> + :doc: Extended Format Pointer Specifiers
> +
> +
> +Plain Pointers
> +--------------
>
> ::
>
> %p abcdef12 or 00000000abcdef12
>
> +Pointers printed without a specifier extension (i.e unadorned ``%p``) are
> +hashed to give a unique identifier without leaking kernel addresses to user
> +space. On 64 bit machines the first 32 bits are zeroed. If you *really*
64-bit
> +want the address see ``%px`` below.
> +
> Symbols/Function Pointers
> -=========================
> +-------------------------
>
> ::
>
> @@ -69,61 +104,60 @@ Symbols/Function Pointers
> %ps versatile_init
> %pB prev_fn_of_versatile_init+0x88/0x88
>
> -The ``F`` and ``f`` specifiers are for printing function pointers,
> -for example, f->func, &gettimeofday. They have the same result as
> -``S`` and ``s`` specifiers. But they do an extra conversion on
> -ia64, ppc64 and parisc64 architectures where the function pointers
> -are actually function descriptors.
> +The ``F`` and ``f`` specifiers are for printing function pointers, for
> +example, ``f->func``, ``&gettimeofday``. They have the same result as ``S``
> +and ``s`` specifiers. But they do an extra conversion on ia64, ppc64 and
> +parisc64 architectures where the function pointers are actually function
> +descriptors.
>
> The ``S`` and ``s`` specifiers can be used for printing symbols
> -from direct addresses, for example, __builtin_return_address(0),
> -(void *)regs->ip. They result in the symbol name with (``S``) or
> +from direct addresses, for example, ``__builtin_return_address(0)``,
> +``(void *)regs->ip``. They result in the symbol name with (``S``) or
> without (``s``) offsets. If KALLSYMS are disabled then 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.
> +when tail-call's are used and marked with the ``noreturn`` GCC attribute.
>
> Examples::
>
> printk("Going to call: %pF\n", gettimeofday);
> printk("Going to call: %pF\n", p->func);
> printk("%s: called from %pS\n", __func__, (void *)_RET_IP_);
> - printk("%s: called from %pS\n", __func__,
> - (void *)__builtin_return_address(0));
> + printk("%s: called from %pS\n", __func__, (void *)__builtin_return_address(0));
> printk("Faulted at %pS\n", (void *)regs->ip);
> printk(" %s%pB\n", (reliable ? "" : "? "), (void *)*stack);
>
> Kernel Pointers
> -===============
> +---------------
>
> ::
>
> %pK 01234567 or 0123456789abcdef
>
> 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.
> +users. The behaviour of ``%pK`` depends on the ``kptr_restrict`` sysctl -
> +see ``Documentation/sysctl/kernel.txt`` for more details.
>
> Unmodified Addresses
> -====================
> +--------------------
>
> ::
>
> %px 01234567 or 0123456789abcdef
>
> -For printing pointers when you _really_ want to print the address. Please
> +For printing pointers when you *really* want to print the address. Please
> consider whether or not you are leaking sensitive information about the
> -Kernel layout in memory before printing pointers with %px. %px is
> -functionally equivalent to %lx. %px is preferred to %lx because it is more
> -uniquely grep'able. If, in the future, we need to modify the way the Kernel
> -handles printing pointers it will be nice to be able to find the call
> -sites.
> +kernel memory layout before printing pointers with ``%px``. ``%px`` is
> +functionally equivalent to ``%lx`` (or ``%lu``). ``%px``, however, is
> +preferable because it is more uniquely grep'able. If, in the future, we need
> +to modify the way the Kernel handles printing pointers we will be better
> +equipped to find the call sites.
>
> Struct Resources
> -================
> +----------------
>
> ::
>
> @@ -132,12 +166,13 @@ Struct Resources
> %pR [mem 0x60000000-0x6fffffff pref] or
> [mem 0x0000000060000000-0x000000006fffffff pref]
>
> -For printing struct resources. The ``R`` and ``r`` specifiers result in a
> +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 Address Types ``phys_addr_t``
> +--------------------------------------
>
> ::
>
> @@ -145,20 +180,24 @@ Physical addresses types ``phys_addr_t``
>
> 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.
> +the width of the CPU data path.
> +
> +Passed by reference.
>
> -DMA addresses types ``dma_addr_t``
> -==================================
> +DMA Address 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.
> +regardless of the width of the CPU data path.
>
> -Raw buffer as an escaped string
> -===============================
> +Passed by reference.
> +
> +Raw Buffer as an Escaped String
> +-------------------------------
>
> ::
>
> @@ -168,7 +207,7 @@ 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
> +A few examples show how the conversion would be done (the result string
> without surrounding quotes)::
>
> %*pE "\eb \C\a"\220\r]"
> @@ -194,8 +233,8 @@ printing SSIDs.
>
> If field width is omitted the 1 byte only will be escaped.
then
I think...
>
> -Raw buffer as a hex string
> -==========================
> +Raw Buffer as a Hex String
> +--------------------------
>
> ::
>
> @@ -205,11 +244,11 @@ Raw buffer as a hex string
> %*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
> +certain separator. For the larger buffers consider using
> :c:func:`print_hex_dump`.
>
> -MAC/FDDI addresses
> -==================
> +MAC/FDDI Addresses
> +------------------
>
> ::
>
> @@ -233,8 +272,8 @@ of Bluetooth addresses which are in the little endian order.
>
> Passed by reference.
>
> -IPv4 addresses
> -==============
> +IPv4 Addresses
> +--------------
>
> ::
>
> @@ -252,8 +291,8 @@ no specifier is provided the default network/big endian order is used.
>
> Passed by reference.
>
> -IPv6 addresses
> -==============
> +IPv6 Addresses
> +--------------
>
> ::
>
> @@ -271,8 +310,8 @@ http://tools.ietf.org/html/rfc5952
>
> Passed by reference.
>
> -IPv4/IPv6 addresses (generic, with port, flowinfo, scope)
> -=========================================================
> +IPv4/IPv6 Addresses (generic, with port, flowinfo or scope)
> +---------------------------------------------------------------
I prefer the additional (Oxford) comma.
and why is the --- line longer than the header?
>
> ::
>
> @@ -282,8 +321,8 @@ IPv4/IPv6 addresses (generic, with port, flowinfo, scope)
> %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``,
> +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
> @@ -308,8 +347,8 @@ Further examples::
> %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
> +-------------------
>
> ::
>
> @@ -318,18 +357,18 @@ UUID/GUID addresses
> %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 digits - and big endian order
> +in lower (``b``) or upper case (``B``) hex digits.
>
> Where no additional specifiers are used the default big endian
> -order with lower case hex characters will be printed.
> +order with lower case hex digits will be printed.
digits could imply base 10. but no big deal.
>
> Passed by reference.
>
> -dentry names
> -============
> +Dentry Names
> +------------
>
> ::
>
> @@ -343,24 +382,24 @@ equivalent of ``%s`` ``dentry->d_name.name`` we used to use, ``%pd<n>`` prints
>
> 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
> -================
> +----------------
>
> ::
>
> %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;
> @@ -370,36 +409,33 @@ and va_list as follows::
> Implements a "recursive vsnprintf".
>
> Do not use this feature without some mechanism to verify the
> -correctness of the format string and va_list arguments.
> +correctness of the format string and ``va_list`` arguments.
>
> Passed by reference.
>
> kobjects
> -========
> -
> +--------
> +
> ::
>
> - %pO
> + %pOF[fnpPcCF]
>
> - Base specifier for kobject based structs. Must be followed with
> - character for specific type of kobject as listed below:
>
> - Device tree nodes:
> +For printing kobject based structs (device nodes). Default behaviour is
> +equivalent to ``%pOFf``.
>
> - %pOF[fnpPcCF]
> + - ``f`` device node full_name
> + - ``n`` device node name
> + - ``p`` device node phandle
> + - ``P`` device node path spec (name + @unit)
> + - ``F`` device node flags
> + - ``c`` major compatible string
> + - ``C`` full compatible string
>
> - For printing device tree nodes. The optional arguments are:
> - f device node full_name
> - n device node name
> - p device node phandle
> - P device node path spec (name + @unit)
> - F device node flags
> - c major compatible string
> - C full compatible string
> - Without any arguments prints full_name (same as %pOFf)
> - The separator when using multiple arguments is ':'
> +The separator when using multiple arguments is ``:``
>
> - Examples:
> +Examples:
> +::
>
> %pOF /foo/bar@0 - Node full name
> %pOFf /foo/bar@0 - Same as above
> @@ -412,11 +448,10 @@ kobjects
> P - Populated
> B - Populated bus
>
> - Passed by reference.
> -
> +Passed by reference.
>
> struct clk
> -==========
> +----------
>
> ::
>
> @@ -424,14 +459,14 @@ struct clk
> %pCn pll1
> %pCr 1560000000
>
> -For printing struct clk structures. ``%pC`` and ``%pCn`` print the name
> +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
> -=======================================================
> +Bitmap and its Derivatives (such as cpumask and nodemask)
> +---------------------------------------------------------
>
> ::
>
> @@ -439,13 +474,13 @@ bitmap and its derivatives such as cpumask and nodemask
> %*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.
> +``%*pb`` outputs the bitmap with field width as the number of bits and ``%*pbl``
> +outputs the bitmap as range list with field width as the number of bits.
>
> Passed by reference.
>
> -Flags bitfields such as page flags, gfp_flags
> -=============================================
> +Flags Bitfields (such as page flags, gfp_flags)
> +-----------------------------------------------
>
> ::
>
> @@ -459,25 +494,27 @@ 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 :c:func:`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 the
> +:c:func:`TP_printk()` part of a tracepoint. Instead, use the
> +``show_*_flags()`` functions from ``<trace/events/mmflags.h>``.
>
> Passed by reference.
>
> -Network device features
> -=======================
> +Network Device Features
> +-----------------------
>
> ::
>
> %pNF 0x000000000000c000
>
> -For printing netdev_features_t.
> +For printing ``netdev_features_t``.
>
> 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.
> +Thanks
> +======
>
> +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.
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 01c3957b2de6..f9247b78e8ef 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1727,115 +1727,73 @@ static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
> return number(buf, end, hashval, spec);
> }
>
> +/**
> + * DOC: Extended Format Pointer Specifiers
> + *
> + * Briefly we handle the following extensions:
> + *
> + * - ``F`` - For symbolic function descriptor pointers with offset.
> + * - ``f`` - For simple symbolic function names without offset.
> + *
> + * - ``S`` - For symbolic direct pointers with offset.
> + * - ``s`` - For symbolic direct pointers without offset.
> + * - ``[FfSs]R`` - As above with ``__builtin_extract_return_addr()`` translation.
> + * - ``B`` - For backtraced symbolic direct pointers with offset.
> + * - ``R`` - For decoded struct resource, e.g., [mem 0x0-0x1f 64bit pref].
> + * - ``r`` - For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201].
> + * - ``b[l]`` - For a bitmap, the number of bits is determined by the field
> + * width which must be explicitly specified either as part of the format
> + * string ``32b[l]`` or through ``*b[l]``, ``[l]`` selects range-list format
> + * instead of hex format.
> + * - ``M`` - For a 6-byte MAC address, it prints the address in the usual
> + * colon-separated hex notation.
> + * - ``m`` - For a 6-byte MAC address, it prints the hex address without colons.
> + * - ``MF`` - For a 6-byte MAC FDDI address, it prints the address with a
> + * dash-separated hex notation.
> + * - ``[mM]R`` - For a 6-byte MAC address, Reverse order (Bluetooth).
> + * - ``I[46]`` - For IPv4/IPv6 addresses printed in the usual way.
> + * - ``I[S][pfs]`` - For generic IPv4/IPv6 address (struct sockaddr *) that falls
> + * back to ``[4]`` or ``[6]`` and is able to print port ``[p]``,
> + * flowinfo ``[f]``, scope ``[s]``.
> + * - ``i[46]`` - For 'raw' IPv4/IPv6 addresses IPv6 omits the colons (01020304...0f)
> + * IPv4 uses dot-separated decimal with leading 0's (010.123.045.006).
> + * - ``i[S][pfs]`` - For generic IPv4/IPv6 address (struct sockaddr *) that falls back
> + * to ``[4]`` or ``[6]`` (``[pfs]`` as above).
> + * - ``[Ii][4S][hnbl]`` - For IPv4 addresses in host, network, big or little endian order.
> + * - ``I[6S]c`` - For IPv6 addresses printed as per http://tools.ietf.org/html/rfc5952.
> + * - ``E[achnops]`` - For an escaped buffer.
> + * - ``U`` - For a 16 byte UUID/GUID.
> + * - ``V`` - For a ``struct va_format`` which contains a format ``string *``
> + * and ``va_list *``.
> + * - ``K`` - For a kernel pointer that should be hidden from unprivileged users.
> + * - ``NF`` - For a ``netdev_features_t``.
> + * - ``h[CDN]`` - For a variable-length buffer.
> + * - ``a[pd]`` - For address types ``[p] phys_addr_t``, ``[d] dma_addr_t`` and
> + * derivatives.
> + * - ``d[234]`` - For a dentry name (optionally 2-4 last components).
> + * - ``D[234]`` - Same as 'd' but for a struct file.
> + * - ``g`` - For ``block_device`` name (gendisk + partition number).
> + * - ``C[n]`` - For a clock, it prints the name (Common Clock Framework) or
> + * address (legacy clock framework) of the clock. ``[n]`` is optional.
> + * - ``Cr`` - For a clock, it prints the current rate of the clock.
> + * - ``G`` - For flags to be printed as a collection of symbolic strings that
> + * would construct the specific value.
> + * - ``O`` - For a kobject based struct (device node).
> + * - ``x`` - For printing the address. Equivalent to ``%lx``.
> + */
> +
> /*
> * Show a '%p' thing. A kernel extension is that the '%p' is followed
> * by an extra set of alphanumeric characters that are extended format
> * specifiers.
> *
> + * Please see Documentation/printk-formats.rst for fuller description
> + * of specifier extensions. Also please update this file when making
"this file" is the file that I am reading? or could it be "that file"?
> + * changes.
> + *
> * Please update scripts/checkpatch.pl when adding/removing conversion
> * characters. (Search for "check for vsprintf extension").
> *
> - * Right now we handle:
> - *
> - * - 'F' For symbolic function descriptor pointers with offset
> - * - 'f' For simple symbolic function names without offset
> - * - 'S' For symbolic direct pointers with offset
> - * - 's' For symbolic direct pointers without offset
> - * - '[FfSs]R' as above with __builtin_extract_return_addr() translation
> - * - 'B' For backtraced symbolic direct pointers with offset
> - * - 'R' For decoded struct resource, e.g., [mem 0x0-0x1f 64bit pref]
> - * - 'r' For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201]
> - * - 'b[l]' For a bitmap, the number of bits is determined by the field
> - * width which must be explicitly specified either as part of the
> - * format string '%32b[l]' or through '%*b[l]', [l] selects
> - * range-list format instead of hex format
> - * - 'M' For a 6-byte MAC address, it prints the address in the
> - * usual colon-separated hex notation
> - * - 'm' For a 6-byte MAC address, it prints the hex address without colons
> - * - 'MF' For a 6-byte MAC FDDI address, it prints the address
> - * with a dash-separated hex notation
> - * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
> - * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
> - * IPv4 uses dot-separated decimal without leading 0's (1.2.3.4)
> - * IPv6 uses colon separated network-order 16 bit hex with leading 0's
> - * [S][pfs]
> - * Generic IPv4/IPv6 address (struct sockaddr *) that falls back to
> - * [4] or [6] and is able to print port [p], flowinfo [f], scope [s]
> - * - 'i' [46] for 'raw' IPv4/IPv6 addresses
> - * IPv6 omits the colons (01020304...0f)
> - * IPv4 uses dot-separated decimal with leading 0's (010.123.045.006)
> - * [S][pfs]
> - * Generic IPv4/IPv6 address (struct sockaddr *) that falls back to
> - * [4] or [6] and is able to print port [p], flowinfo [f], scope [s]
> - * - '[Ii][4S][hnbl]' IPv4 addresses in host, network, big or little endian order
> - * - 'I[6S]c' for IPv6 addresses printed as specified by
> - * http://tools.ietf.org/html/rfc5952
> - * - 'E[achnops]' For an escaped buffer, where rules are defined by combination
> - * of the following flags (see string_escape_mem() 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.
> - * - 'U' For a 16 byte UUID/GUID, it prints the UUID/GUID in the form
> - * "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
> - * Options for %pU are:
> - * b big endian lower case hex (default)
> - * B big endian UPPER case hex
> - * l little endian lower case hex
> - * L little endian UPPER case hex
> - * big endian output byte order is:
> - * [0][1][2][3]-[4][5]-[6][7]-[8][9]-[10][11][12][13][14][15]
> - * little endian output byte order is:
> - * [3][2][1][0]-[5][4]-[7][6]-[8][9]-[10][11][12][13][14][15]
> - * - 'V' For a struct va_format which contains a format string * and va_list *,
> - * call vsnprintf(->format, *->va_list).
> - * Implements a "recursive vsnprintf".
> - * Do not use this feature without some mechanism to verify the
> - * correctness of the format string and va_list arguments.
> - * - 'K' For a kernel pointer that should be hidden from unprivileged users
> - * - 'NF' For a netdev_features_t
> - * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
> - * a certain separator (' ' by default):
> - * C colon
> - * D dash
> - * N no separator
> - * The maximum supported length is 64 bytes of the input. Consider
> - * to use print_hex_dump() for the larger input.
> - * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives
> - * (default assumed to be phys_addr_t, passed by reference)
> - * - 'd[234]' For a dentry name (optionally 2-4 last components)
> - * - 'D[234]' Same as 'd' but for a struct file
> - * - 'g' For block_device name (gendisk + partition number)
> - * - 'C' For a clock, it prints the name (Common Clock Framework) or address
> - * (legacy clock framework) of the clock
> - * - 'Cn' For a clock, it prints the name (Common Clock Framework) or address
> - * (legacy clock framework) of the clock
> - * - 'Cr' For a clock, it prints the current rate of the clock
> - * - 'G' For flags to be printed as a collection of symbolic strings that would
> - * construct the specific value. Supported flags given by option:
> - * p page flags (see struct page) given as pointer to unsigned long
> - * g gfp flags (GFP_* and __GFP_*) given as pointer to gfp_t
> - * v vma flags (VM_*) given as pointer to unsigned long
> - * - 'O' For a kobject based struct. Must be one of the following:
> - * - 'OF[fnpPcCF]' For a device tree object
> - * Without any optional arguments prints the full_name
> - * f device node full_name
> - * n device node name
> - * p device node phandle
> - * P device node path spec (name + @unit)
> - * F device node flags
> - * c major compatible string
> - * C full compatible string
> - *
> - * - 'x' For printing the address. Equivalent to "%lx".
> - *
> - * ** Please update also Documentation/printk-formats.txt when making changes **
> - *
> * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
> * function pointers are really function descriptors, which contain a
> * pointer to the real address.
>
ta.
--
~Randy
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