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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