Re: [PATCH V2 1/3] clk: add clk_bulk_get accessories

[Geert Uytterhoeven]

Hi Dong,

On Mon, May 8, 2017 at 4:03 PM, Dong Aisheng <aisheng.dong@xxxxxxx> wrote:
> --- /dev/null
> +++ b/drivers/clk/clk-bulk.c
> @@ -0,0 +1,165 @@

> +int __must_check clk_bulk_get(struct device *dev, int num_clks,
> +                             struct clk_bulk_data *clks)
> +{
> +       int ret;
> +       int i;
> +
> +       for (i = 0; i < num_clks; i++)
> +               clks[i].clk = NULL;
> +
> +       for (i = 0; i < num_clks; i++) {
> +               clks[i].clk = clk_get(dev, clks[i].id);
> +               if (IS_ERR(clks[i].clk)) {
> +                       ret = PTR_ERR(clks[i].clk);
> +                       dev_err(dev, "Failed to get clk '%s': %d\n",
> +                               clks[i].id, ret);
> +                       clks[i].clk = NULL;
> +                       goto err;
> +               }
> +       }
> +
> +       return 0;
> +
> +err:
> +       while (--i >= 0)
> +               clk_put(clks[i].clk);

These are released in inverse order, which is good.

> +
> +       return ret;
> +}
> +EXPORT_SYMBOL(clk_bulk_get);
> +
> +void clk_bulk_put(int num_clks, struct clk_bulk_data *clks)
> +{
> +       int i;
> +
> +       for (i = 0; i < num_clks; i++) {
> +               clk_put(clks[i].clk);
> +               clks[i].clk = NULL;

These aren't.

Typically resources are released in the inverse order. Not doing so may
cause subtle issues.

I can't come up with an example. but I'm quite sure the real world will find
one soon ;-)

The same is true for enable vs. disable, and prepare vs. unprepare.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds