大家帮我看看clk_get究竟是怎么实现的。谢谢

[pcwung]

linux-2.6.21.5/arch/arm/plat-s3c24xx/clock.c
/* Clock API calls */

struct clk *(struct device *dev, const char *id)
{
    struct clk *p;
    struct clk *clk = ERR_PTR(-ENOENT);
    int idno;

    if (dev == NULL || dev->bus != &platform_bus_type)
        idno = -1;
    else
        idno = to_platform_device(dev)->id;

    mutex_lock(&clocks_mutex);

    list_for_each_entry(p, & clocks, list) {
        if (p->id == idno &&
            strcmp(id, p->name) == 0 &&
            try_module_get(p->owner)) {
            clk = p;
            break;
        }
    }

    /* check for the case where a device was supplied, but the
     * clock that was being searched for is not device specific */

    if (IS_ERR(clk)) {
        list_for_each_entry(p, &clocks, list) {
            if (p->id == -1 && strcmp(id, p->name) == 0 &&
                try_module_get(p->owner)) {
                clk = p;
                break;
            }
        }
    }

    mutex_unlock(&clocks_mutex);
    return clk;
}

#define list_for_each_entry(pos, head, member)                \
for (pos = list_entry((head)->next, typeof(*pos), member);    \
prefetch(pos->member.next), &pos->member != (head);     \
pos = list_entry(pos->member.next, typeof(*pos), member))

说白了define list_for_each_entry 就是一个for循环。。。。

怎么和

struct clk clk_xtal = {
.name   = "xtal",
.id   = -1,
.rate   = 0,
.parent   = NULL,
.ctrlbit = 0,
};

这些结构体联系起来的呢？？？

[pcwung]

struct clk {
    struct list_head node;
    const char    *name;        /* unique clock name */
    const char    *function;    /* function of the clock */
    struct device    *dev;        /* device associated with function */
    unsigned long    rate_hz;
    struct clk    *parent;
    u32        pmc_mask;
    void        (*mode)(struct clk *, int);
    unsigned    id:2;        /* PCK0..3, or 32k/main/a/b */
    unsigned    type;        /* clock type */
    u16        users;
};

static struct clk isi_clk = {
    .name        = "isi_clk",
    .pmc_mask    = 1 << AT91CAP9_ID_ISI,
    .type        = CLK_TYPE_PERIPHERAL,
};


static void __clk_enable(struct clk *clk)
{
    if (clk->parent)
        __clk_enable(clk->parent);
    if (clk->users++ == 0 && clk->mode)
        clk->mode(clk, 1);
}

int clk_enable(struct clk *clk)
{
    unsigned long    flags;

    spin_lock_irqsave(&clk_lock, flags);
    __clk_enable(clk);
    spin_unlock_irqrestore(&clk_lock, flags);
    return 0;
}
EXPORT_SYMBOL(clk_enable);


/* Register a new clock */
int __init clk_register(struct clk *clk)
{
    if (clk_is_peripheral(clk)) {
        clk->parent = &mck;
        clk->mode = pmc_periph_mode;
        list_add_tail(&clk->node, &clocks);
    }
    else if (clk_is_sys(clk)) {
        clk->parent = &mck;
        clk->mode = pmc_sys_mode;

        list_add_tail(&clk->node, &clocks);
    }
#ifdef CONFIG_AT91_PROGRAMMABLE_CLOCKS
    else if (clk_is_programmable(clk)) {
        clk->mode = pmc_sys_mode;
        init_programmable_clock(clk);
        list_add_tail(&clk->node, &clocks);
    }
#endif

    return 0;
}


/*
 * Several unused clocks may be active.  Turn them off.
 */
static int __init at91_clock_reset(void)
{
    unsigned long pcdr = 0;
    unsigned long scdr = 0;
    struct clk *clk;

    list_for_each_entry(clk, &clocks, node) {
        if (clk->users > 0)
            continue;

        if (clk->mode == pmc_periph_mode)
            pcdr |= clk->pmc_mask;

        if (clk->mode == pmc_sys_mode)
            scdr |= clk->pmc_mask;

        pr_debug("Clocks: disable unused %s\n", clk->name);
    }

    at91_sys_write(AT91_PMC_PCDR, pcdr);
    at91_sys_write(AT91_PMC_SCDR, scdr);

    return 0;
}
late_initcall(at91_clock_reset);


static void pmc_periph_mode(struct clk *clk, int is_on)
{
    if (is_on)
        at91_sys_write(AT91_PMC_PCER, clk->pmc_mask);
    else
        at91_sys_write(AT91_PMC_PCDR, clk->pmc_mask);
}