linux-kernel - Re: [PATCH] dyn_array: using %pF instead of print_fn_descriptor

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Date:	Fri, 29 Aug 2008 15:32:58 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dyn_array: using %pF instead of print_fn_descriptor_symbol

On Fri, Aug 29, 2008 at 3:20 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Fri, 29 Aug 2008 15:07:49 -0700
> Yinghai Lu <yhlu.kernel@...il.com> wrote:
>
>> +             printk(KERN_DEBUG "per_cpu_dyn_array %pF ==> [%#lx - %#lx]\n",
>> +                     da->name, phys, phys + size);
>
> This:
>
> struct dyn_array {
>        void **name;
>
> is a bit confusing.  One normally expects a variable called "name" to
> point at a character string.
>
> What _does_ this thing point at?  There are no code comments which I
> can find, it's unobvious from the source code, the type is the
> information-free void** and the identifier is misleading.
>
> I find that documenting the data structures is the best way of making
> code understandable (and hence maintainable).

struct dyn_array {
        void **name;
        unsigned long size;
        unsigned int *nr;
        unsigned long align;
        void (*init_work)(void *);
};
extern struct dyn_array *__dyn_array_start[], *__dyn_array_end[];
extern struct dyn_array *__per_cpu_dyn_array_start[],
*__per_cpu_dyn_array_end[];

#define DEFINE_DYN_ARRAY_ADDR(nameX, addrX, sizeX, nrX, alignX, init_workX) \
                static struct dyn_array __dyn_array_##nameX __initdata = \
                {       .name = (void **)&(nameX),\
                        .size = sizeX,\
                        .nr   = &(nrX),\
                        .align = alignX,\
                        .init_work = init_workX,\
                }; \
                static struct dyn_array *__dyn_array_ptr_##nameX __used \
                __attribute__((__section__(".dyn_array.init"))) = \
                        &__dyn_array_##nameX

#define DEFINE_DYN_ARRAY(nameX, sizeX, nrX, alignX, init_workX) \
        DEFINE_DYN_ARRAY_ADDR(nameX, nameX, sizeX, nrX, alignX, init_workX)

and use is

struct irq_desc *sparse_irqs;
DEFINE_DYN_ARRAY(sparse_irqs, sizeof(struct irq_desc), nr_irq_desc,
PAGE_SIZE, init_work);


then sparse_irqs is pointer, and .name store the address of that pointer.

later use
*da->name = phys_to_virt(phys);
to take back the dyn address.

YH
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