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

yalin wang
2015-12-04T01:04:35Z

>> 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, ‘|’)
a little change:
#define VMA_FLAG_FORMAT(vma) FLAG_FORMAT(vma->vm_flags, vmaflags_names, ‘|’)

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

>
> that’s 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.*%x’ .
> it will be great if this flag string print is generic.
>
> Thanks