linux-kernel - Re: [PATCH 1/2] clk: Fix error handling in fixed clock hardware type register fn

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Date:	Tue, 20 Mar 2012 00:46:04 -0700 (PDT)
From:	"Saravana Kannan" <skannan@...eaurora.org>
To:	"Sascha Hauer" <s.hauer@...gutronix.de>
Cc:	"Saravana Kannan" <skannan@...eaurora.org>,
	"Mike Turquette" <mturquette@...aro.org>,
	"Arnd Bergman" <arnd.bergmann@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, "Andrew Lunn" <andrew@...n.ch>,
	"Rob Herring" <rob.herring@...xeda.com>,
	"Russell King" <linux@....linux.org.uk>,
	"Jeremy Kerr" <jeremy.kerr@...onical.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Paul Walmsley" <paul@...an.com>,
	"Shawn Guo" <shawn.guo@...escale.com>,
	"Jamie Iles" <jamie@...ieiles.com>,
	"Richard Zhao" <richard.zhao@...aro.org>,
	"Magnus Damm" <magnus.damm@...il.com>,
	"Mark Brown" <broonie@...nsource.wolfsonmicro.com>,
	"Linus Walleij" <linus.walleij@...ricsson.com>,
	"Stephen Boyd" <sboyd@...eaurora.org>,
	"Amit Kucheria" <amit.kucheria@...aro.org>,
	"Deepak Saxena" <dsaxena@...aro.org>,
	"Grant Likely" <grant.likely@...retlab.ca>
Subject: Re: [PATCH 1/2] clk: Fix error handling in fixed clock hardware 
     type register fn


On Tue, March 20, 2012 12:19 am, Sascha Hauer wrote:
> On Mon, Mar 19, 2012 at 08:38:25PM -0700, Saravana Kannan wrote:
>> If memory allocation for the parents array or the parent string fails,
>> then
>> fail the registration immediately instead of calling clk_register and
>> hoping it fails there.
>>
>> Return -ENOMEM on failure.
>>
>> Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
>> Cc: Mike Turquette <mturquette@...aro.org>
>> Cc: Andrew Lunn <andrew@...n.ch>
>> Cc: Rob Herring <rob.herring@...xeda.com>
>> Cc: Russell King <linux@....linux.org.uk>
>> Cc: Jeremy Kerr <jeremy.kerr@...onical.com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Arnd Bergman <arnd.bergmann@...aro.org>
>> Cc: Paul Walmsley <paul@...an.com>
>> Cc: Shawn Guo <shawn.guo@...escale.com>
>> Cc: Sascha Hauer <s.hauer@...gutronix.de>
>> Cc: Jamie Iles <jamie@...ieiles.com>
>> Cc: Richard Zhao <richard.zhao@...aro.org>
>> Cc: Saravana Kannan <skannan@...eaurora.org>
>> Cc: Magnus Damm <magnus.damm@...il.com>
>> Cc: Mark Brown <broonie@...nsource.wolfsonmicro.com>
>> Cc: Linus Walleij <linus.walleij@...ricsson.com>
>> Cc: Stephen Boyd <sboyd@...eaurora.org>
>> Cc: Amit Kucheria <amit.kucheria@...aro.org>
>> Cc: Deepak Saxena <dsaxena@...aro.org>
>> Cc: Grant Likely <grant.likely@...retlab.ca>
>> ---
>> There are still some memory free issues when clk_register() fails, but I
>> will
>> fix it when I fixed the other register() fns to return ENOMEM of alloc
>> failure instead of a NULL.
>>
>>  drivers/clk/clk-fixed-rate.c |   10 +++++++---
>>  1 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/clk/clk-fixed-rate.c b/drivers/clk/clk-fixed-rate.c
>> index 90c79fb..6423ae9 100644
>> --- a/drivers/clk/clk-fixed-rate.c
>> +++ b/drivers/clk/clk-fixed-rate.c
>> @@ -61,22 +61,26 @@ struct clk *clk_register_fixed_rate(struct device
>> *dev, const char *name,
>>  		parent_names = kmalloc(sizeof(char *), GFP_KERNEL);
>>
>>  		if (! parent_names)
>> -			goto out;
>> +			goto fail_ptr;
>>
>>  		len = sizeof(char) * strlen(parent_name);
>>
>>  		parent_names[0] = kmalloc(len, GFP_KERNEL);
>>
>>  		if (!parent_names[0])
>> -			goto out;
>> +			goto fail_str;
>>
>>  		strncpy(parent_names[0], parent_name, len);
>>  	}
>
> It's easier to add a char *parent to struct clk_fixed and pass it to
> clk_register with &fixed->parent. This saves you a kmalloc call and
> makes the error path simpler. It's the same way already done in the
> divider.

I thought about that since I saw the same was done for gated and divider
(I think). Here is my guess at Mike's reasoning for this:

Gated and divider clocks have to have a parent. There's nothing to gate
otherwise. But fixed rate clocks might not have a parent. It could be XO's
or PLLs running off of always on XOs not controlled by the SoC. So, it's
arguable to not have a parent. I don't have a strong opinion on this --
since Mike took the time to write it, it left it to his subjective
preference.

I sent this patch first since it was around the place I was cleaning up. I
didn't want to actually just shuffle around a bug. As I mentioned, this
patch still leaves a bug open -- what if clk_register() fails. I plan to
fix that once my two patches are picked up (hopefully).

Thanks,
Saravana

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.


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