linux-kernel - Re: [PATCH] PM / OPP: Add dev_pm_opp_{set|put}

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Date:   Tue, 20 Jun 2017 14:08:20 -0700
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / OPP: Add dev_pm_opp_{set|put}_clkname()

On 06/20, Viresh Kumar wrote:
> + */
> +struct opp_table *dev_pm_opp_set_clkname(struct device *dev, const char *name)
> +{
> +	struct opp_table *opp_table;
> +	int ret;
> +
> +	opp_table = dev_pm_opp_get_opp_table(dev);
> +	if (!opp_table)
> +		return ERR_PTR(-ENOMEM);
> +
> +	/* This should be called before OPPs are initialized */
> +	if (WARN_ON(!list_empty(&opp_table->opp_list))) {
> +		ret = -EBUSY;
> +		goto err;
> +	}
> +
> +	/* Already have clkname set */
> +	if (opp_table->clk_name) {
> +		ret = -EBUSY;
> +		goto err;
> +	}
> +
> +	opp_table->clk_name = kstrdup(name, GFP_KERNEL);
> +	if (!opp_table->clk_name) {

Is there a reason to duplicate clk_name instead of using the clk
structure returned from clk_get()? Is it because we may already
have opp_table->clk set from default init? Why can't we always
clk_put() the clk structure if it's !IS_ERR() and then allow
dev_pm_opp_set_clkname() to be called many times in succession?
Long story short, I don't see the benefit to allocating the name
again here just to use it as a mechanism to know if the APIs have
been called symmetrically.

> +		ret = -ENOMEM;
> +		goto err;
> +	}
> +
> +	/* Already have default clk set, free it */
> +	if (!IS_ERR(opp_table->clk))
> +		clk_put(opp_table->clk);
> +

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