Messages in this thread | | | Date | Sat, 10 Dec 2016 09:50:09 +1100 (AEDT) | From | Finn Thain <> | Subject | Re: [PATCH 18/22] m68k/mm: kmap - Modernize printing of kernel messages |
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On Thu, 8 Dec 2016, I wrote:
> > On Wed, 7 Dec 2016, Geert Uytterhoeven wrote: > > > - Convert from printk() to pr_*(), > > - Add missing continuations, > > - Remove #undef DEBUG. > > > > Note that "#ifdef DEBUG" is sometimes retained because pr_cont() is > > not optimized away when debugging is disabled. > > > > I think that argues for using printk(KERN_DEBUG ...) and print(KERN_CONT > ...) inside #ifdef DEBUG, which would need no explanation. > > If instead you use a combination of pr_debug and pr_cont and #ifdef > DEBUG, perhaps the explanation should be moved from the commit log to a > comment in the code? >
Perhaps a better solution than these alternatives would be,
#if defined(DEBUG) #define pr_debug_cont pr_cont #else #define pr_debug_cont no_printk #endif
But this API is still surprising and ugly. It doesn't work with CONFIG_DYNAMIC_DEBUG but that's not so important.
IMO, a far better linux/printk.h would have provided us with these definitions:
#define pr_emerg(fmt, ...) \ printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) /* ... */ #define pr_debug(fmt, ...) \ printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #define pr_cont(fmt, ...) \ printk(KERN_CONT fmt, ##__VA_ARGS__)
#if defined(CONFIG_DYNAMIC_DEBUG) #define pr_debug_cond(fmt, ...) \ dynamic_pr_debug(fmt, ##__VA_ARGS__) #define pr_cont_cond(fmt, ...) \ dynamic_pr_cont(fmt, ##__VA_ARGS__) #elif defined(DEBUG) #define pr_debug_cond(fmt, ...) \ printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #define pr_cont_cond(fmt, ...) \ no_printk(KERN_CONT pr_fmt(fmt), ##__VA_ARGS__) #else #define pr_debug_cond(fmt, ...) \ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #define pr_cont_cond(fmt, ...) \ no_printk(KERN_CONT pr_fmt(fmt), ##__VA_ARGS__) #endif
Which have the virtues of symmetry and least surprise.
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