linux-kernel - Re: [PATCH V2 1/3] clk: add clk_bulk

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Date:   Mon, 8 May 2017 17:08:46 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Dong Aisheng <aisheng.dong@....com>
Cc:     linux-clk <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Mark Brown <broonie@...nel.org>, yibin.gong@....com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>, anson.huang@....com,
        ping.bai@....com, Leonard Crestez <leonard.crestez@....com>,
        octavian.purdila@....com, Russell King <linux@...linux.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH V2 1/3] clk: add clk_bulk_get accessories

Hi Dong,

On Mon, May 8, 2017 at 4:03 PM, Dong Aisheng <aisheng.dong@....com> 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@...ux-m68k.org

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