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| author | Hector Martin <marcan@marcan.st> | 2025-04-08 12:17:57 +0530 |
|---|---|---|
| committer | Alyssa Rosenzweig <alyssa@rosenzweig.io> | 2025-04-21 10:18:30 -0400 |
| commit | 1938479b2720ebc05aab349c7dc0a53921ff7c87 (patch) | |
| tree | 50e0898160d692b9e70a3c3e705ac29ceceec630 /Documentation/core-api | |
| parent | 729f8eefdcadaff98606931e691910f17d8d59d6 (diff) | |
| download | linux-1938479b2720ebc05aab349c7dc0a53921ff7c87.tar.gz linux-1938479b2720ebc05aab349c7dc0a53921ff7c87.tar.bz2 linux-1938479b2720ebc05aab349c7dc0a53921ff7c87.zip | |
lib/vsprintf: Add support for generic FourCCs by extending %p4cc
%p4cc is designed for DRM/V4L2 FourCCs with their specific quirks, but
it's useful to be able to print generic 4-character codes formatted as
an integer. Extend it to add format specifiers for printing generic
32-bit FourCCs with various endian semantics:
%p4ch Host byte order
%p4cn Network byte order
%p4cl Little-endian
%p4cb Big-endian
The endianness determines how bytes are interpreted as a u32, and the
FourCC is then always printed MSByte-first (this is the opposite of
V4L/DRM FourCCs). This covers most practical cases, e.g. %p4cn would
allow printing LSByte-first FourCCs stored in host endian order
(other than the hex form being in character order, not the integer
value).
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Aditya Garg <gargaditya08@live.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/PN3PR01MB9597B01823415CB7FCD3BC27B8B52@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 4bdc394e86af..125fd0397510 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -648,6 +648,38 @@ Examples:: %p4cc Y10 little-endian (0x20303159) %p4cc NV12 big-endian (0xb231564e) +Generic FourCC code +------------------- + +:: + %p4c[hnlb] gP00 (0x67503030) + +Print a generic FourCC code, as both ASCII characters and its numerical +value as hexadecimal. + +The generic FourCC code is always printed in the big-endian format, +the most significant byte first. This is the opposite of V4L/DRM FourCCs. + +The additional ``h``, ``n``, ``l``, and ``b`` specifiers define what +endianness is used to load the stored bytes. The data might be interpreted +using the host byte order, network byte order, little-endian, or big-endian. + +Passed by reference. + +Examples for a little-endian machine, given &(u32)0x67503030:: + + %p4ch gP00 (0x67503030) + %p4cn 00Pg (0x30305067) + %p4cl gP00 (0x67503030) + %p4cb 00Pg (0x30305067) + +Examples for a big-endian machine, given &(u32)0x67503030:: + + %p4ch gP00 (0x67503030) + %p4cn 00Pg (0x30305067) + %p4cl 00Pg (0x30305067) + %p4cb gP00 (0x67503030) + Rust ---- |