netdev - Re: [PATCH V2 01/14] clk: add helper functions clk_prepare_enable and clk_disable

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Date:	Fri, 11 Nov 2011 09:49:50 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Richard Zhao <richard.zhao@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
	linux-mmc@...r.kernel.org, netdev@...r.kernel.org,
	linux-serial@...r.kernel.org, linux@....linux.org.uk,
	amit.kucheria@...onical.com, kernel@...gutronix.de,
	ben-linux@...ff.org, cjb@...top.org, alan@...ux.intel.com,
	eric.miao@...aro.org
Subject: Re: [PATCH V2 01/14] clk: add helper functions clk_prepare_enable
 and clk_disable_unprepare

On Fri, Nov 11, 2011 at 09:10:16AM +0800, Richard Zhao wrote:
> Signed-off-by: Richard Zhao <richard.zhao@...aro.org>
> ---
>  include/linux/clk.h |   19 +++++++++++++++++++
>  1 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index 7213b52..63985f7 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -107,6 +107,25 @@ static inline void clk_unprepare(struct clk *clk)
>  }
>  #endif
>  
> +static inline int clk_prepare_enable(struct clk *clk)
> +{
> +	int ret;
> +
> +	ret = clk_prepare(clk);
> +	if (!ret)
> +		ret = clk_enable(clk);
> +	if (ret)
> +		clk_unprepare(clk);

As Baruch already pointed out this is hard to read. Also it contains a
bug. When clk_prepare fails clk_unprepare is called afterwards.

Hint: Kernel guys are not afraid of having multiple return statements
in a function, instead they like it when something is handled early
without having to read the rest of the function.

Sascha

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