From b67ad18b06701b77ca8bfe9bb760c5c9e765e3cf Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Wed, 12 Nov 2008 13:26:55 -0800 Subject: [PATCH] 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. Signed-off-by: Randy Dunlap Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/00-INDEX | 2 ++ Documentation/printk-formats.txt | 35 ++++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+) create mode 100644 Documentation/printk-formats.txt diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX index edef85ce1195..50f99eab0e1f 100644 --- a/Documentation/00-INDEX +++ b/Documentation/00-INDEX @@ -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 diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt new file mode 100644 index 000000000000..1b5a5ddbc3ef --- /dev/null +++ b/Documentation/printk-formats.txt @@ -0,0 +1,35 @@ +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 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 -- 2.20.1