linux-kernel - Re: [PATCH] clk: <linux/clk.h>: correct clk_get

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Message-ID: <9574eefa-84ed-8674-f575-be47d2a51a1c@infradead.org>
Date:   Tue, 27 Apr 2021 10:07:04 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH] clk: <linux/clk.h>: correct clk_get_parent()
 documentation

On 4/27/21 2:38 AM, Russell King - ARM Linux admin wrote:
> On Mon, Apr 26, 2021 at 08:13:42PM -0700, Randy Dunlap wrote:
>> Make the kernel-doc return value agree with both the stub implementation
>> in <linux/clk.h> and the non-stub function in drivers/clk/clk.c.
>>
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>> Cc: Russell King <linux@...linux.org.uk>
>> Cc: linux-clk@...r.kernel.org
>> ---
>> There are several drivers that call clk_get_parent() and use its
>> return value as though it returns an ERR_PTR(). I am working on a
>> patch series to fix those.
> 
> The whole premise of the CLK API is that:
> 
> - clk values that IS_ERR() returns true are errors
> - clk values that IS_ERR() returns false are valid
> 
> and that is that - nice, simple, easy to understand. So the
> documentation is correct. If clk_get_parent() needs to return an
> error, it does so by returning an error-pointer, not by returning
> NULL.

Hm, so the 6 drivers that do this are OK then, if
clk_get_parent() returns NULL?


	parent = clk_get_parent(clk);
	if (IS_ERR(parent)) {
		dev_err(cpu_dev, "Cannot get parent clock for CPU0\n");
		clk_put(clk);
		return PTR_ERR(parent);
	}

	/* Get parent CPU frequency */
	base_frequency =  clk_get_rate(parent);

boom?

-- 
~Randy