linux-kernel - Re: [RFC 3/5] clk: use struct clk only for external API

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Message-ID: <53ADF239.9050008@wwwdotorg.org>
Date:	Fri, 27 Jun 2014 16:37:45 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Mike Turquette <mturquette@...aro.org>,
	Rabin Vincent <rabin.vincent@...ricsson.com>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 3/5] clk: use struct clk only for external API

On 06/27/2014 01:57 AM, Tomeu Vizoso wrote:
> From: Rabin Vincent <rabin.vincent@...ricsson.com>
> 
> In order to provide per-user accounting, this separates the struct clk
> used in the common clock framework into two structures 'struct clk_core'
> and 'struct clk'.  struct clk_core will be used for internal
> manipulation and struct clk will be used in the clock API
> implementation.
> 
> In this patch, struct clk is simply renamed to struct clk_core and a new
> struct clk is implemented which simply wraps it.  In the next patch, the
> new struct clk will be used to implement per-user clock enable
> accounting.

> diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h

> -struct clk {
> +struct clk_core {
>  	const char		*name;
>  	const struct clk_ops	*ops;
>  	struct clk_hw		*hw;
>  	struct module		*owner;
> -	struct clk		*parent;
> +	struct clk_core		*parent;
>  	const char		**parent_names;
> -	struct clk		**parents;
> +	struct clk_core		**parents;
>  	u8			num_parents;
>  	u8			new_parent_index;
>  	unsigned long		rate;
>  	unsigned long		new_rate;
> -	struct clk		*new_parent;
> -	struct clk		*new_child;
> +	struct clk_core		*new_parent;
> +	struct clk_core		*new_child;
>  	unsigned long		flags;
>  	unsigned int		enable_count;
>  	unsigned int		prepare_count;
> @@ -55,6 +55,10 @@ struct clk {
>  	struct kref		ref;
>  };
>  
> +struct clk {
> +	struct clk_core clk;
> +};

I'm confused why that field isn't a pointer instead. Don't we want to
end up with the following data structure:

(dev a's) struct clk --------v
                           struct clk_core -----> struct clk_hw
(dev b's) struct clk --------^

Where all 3 arrows are pointers? (and struct clk_core probably contains
a list of the struct clk that point at it).

Otherwise, we end up creating a whole struct clk_core for each client.
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