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Commit b67ad18b authored by Randy Dunlap's avatar Randy Dunlap Committed by Linus Torvalds
Browse files

DOC: add printk-formats.txt 



Add printk-formats.txt so that we don't have to keep fixing the
same things over and over again.  <wishful thinking>

Signed-off-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b76f90b5

Documentation/00-INDEX

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Original line number Diff line number Diff line
@@ -290,6 +290,8 @@ powerpc/ 
	- directory with info on using Linux with the PowerPC.

preempt-locking.txt

	- info on locking under a preemptive kernel.

printk-formats.txt

	- how to get printk format specifiers right

prio_tree.txt

	- info on radix-priority-search-tree use for indexing vmas.

ramdisk.txt

Documentation/printk-formats.txt

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+35 −0
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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



Raw pointer value SHOULD be printed with %p.



u64 SHOULD be printed with %llu/%llx, (unsigned long long):



	printk("%llu", (unsigned long long)u64_var);



s64 SHOULD be printed with %lld/%llx, (long long):



	printk("%lld", (long long)s64_var);



If <type> is dependent on a config option for its size (e.g., sector_t,

blkcnt_t, phys_addr_t, resource_size_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.



Thank you for your cooperation and attention.





By Randy Dunlap <rdunlap@xenotime.net>