linux-kernel - Re: [PATCH] PM / OPP: Initialize regulator pointer to an error value

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Date:	Mon, 15 Feb 2016 22:13:30 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Rafael Wysocki <rjw@...ysocki.net>,
	Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Jon Hunter <jonathanh@...dia.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] PM / OPP: Initialize regulator pointer to an error value

On Mon, Feb 15, 2016 at 9:38 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Monday 15 February 2016 21:56:42 Viresh Kumar wrote:
>> We are currently required to do two checks for regulator pointer:
>> IS_ERR() and IS_NULL().
>>
>> And multiple instances are reported, about both of these not being used
>> consistently and so resulting in crashes.
>>
>> Fix that by initializing regulator pointer with an error value and
>> checking it only against an error.
>>
>> This makes code consistent and efficient.
>
> There is usually something else wrong if you have to check for both.
> Why exactly do you need to check for both IS_ERR and NULL?
>
>> diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
>> index d7cd4e265766..146b6197d598 100644
>> --- a/drivers/base/power/opp/core.c
>> +++ b/drivers/base/power/opp/core.c
>> @@ -257,7 +257,7 @@ unsigned long dev_pm_opp_get_max_volt_latency(struct device *dev)
>>       }
>>
>>       reg = dev_opp->regulator;
>> -     if (IS_ERR_OR_NULL(reg)) {
>> +     if (IS_ERR(reg)) {
>>               /* Regulator may not be required for device */
>>               if (reg)
>>                       dev_err(dev, "%s: Invalid regulator (%ld)\n", __func__,
>> @@ -798,6 +798,9 @@ static struct device_opp *_add_device_opp(struct device *dev)
>>               of_node_put(np);
>>       }
>>
>> +     /* Set regulator to a non-NULL error value */
>> +     dev_opp->regulator = ERR_PTR(-EFAULT);
>> +
>>       /* Find clk for the device */
>>       dev_opp->clk = clk_get(dev, NULL);
>>       if (IS_ERR(dev_opp->clk)) {
>
> -EFAULT has a very specific meaning (accessing an invalid pointer from
> user space), I don't think you want that one.

Yeah, agreed.

That should be something like -ENXIO IMO.

Thanks,
Rafael