Re: [PATCH 1/2] mm, printk: introduce new format string for flags

[yalin wang]

>> Technically, I think the answer is yes, at least in C99 (and I suppose
>> gcc would accept it in gnu89 mode as well).
>> 
>> printk("%pg\n", &(struct flag_printer){.flags = my_flags, .names = vmaflags_names});
>> 
>> Not tested, and I still don't think it would be particularly readable
>> even when macroized
>> 
>> printk("%pg\n", PRINTF_VMAFLAGS(my_flags));
> i test on gcc 4.9.3, it can work for this method,
> so the final solution like this:
> printk.h:
> struct flag_fmt_spec {
> 	unsigned long flag;
> 	struct trace_print_flags *flags;
> 	int array_size;
> 	char delimiter; }
> 
> #define FLAG_FORMAT(flag, flag_array, delimiter) (&(struct flag_ft_spec){ .flag = flag, .flags = flag_array, .array_size = ARRAY_SIZE(flag_array), .delimiter = delimiter})
> #define VMA_FLAG_FORMAT(flag)  FLAG_FORMAT(flag, vmaflags_names, â|â)
a little change:
	#define VMA_FLAG_FORMAT(vma)  FLAG_FORMAT(vma->vm_flags, vmaflags_names, â|â)


> source code:
> printk("%pg\n", VMA_FLAG_FORMAT(my_flags)); 
a little change:
	printk("%pg\n", VMA_FLAG_FORMAT(vma)); 

> 
> thatâs all, see cpumask_pr_args(masks) macro,
> it also use macro and  %*pb  to print cpu mask .
> i think this method is not very complex to use .
> 
> search source code ,
> there is lots of printk to print flag into hex number :
> $ grep -n  -r 'printk.*flag.*%xâ  .
> it will be great if this flag string print is generic.
> 
> Thanks

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