linux-kernel - Re: [PATCH] PM / QoS: Fix device resume latency PM QoS

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Message-ID: <CAJZ5v0hgnq78z+=msaJjJmSFSHPM06MZ2_iRzixtRRDGxK-yBg@mail.gmail.com>
Date:   Thu, 26 Oct 2017 10:38:10 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>, ramesh.thomas@...el.com,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Alex Shi <alex.shi@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] PM / QoS: Fix device resume latency PM QoS

On Wed, Oct 25, 2017 at 10:06 PM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Tue, Oct 24, 2017 at 11:49 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> On Tuesday, October 24, 2017 7:54:09 AM CEST Ramesh Thomas wrote:
>>> On 2017-10-20 at 13:27:34 +0200, Rafael J. Wysocki wrote:
>
>>> >  static ssize_t pm_qos_resume_latency_store(struct device *dev,
>>> > @@ -228,11 +235,19 @@ static ssize_t pm_qos_resume_latency_sto
>>> >     s32 value;
>>> >     int ret;
>
>>> > +   if (!kstrtos32(buf, 0, &value)) {
>>> > +           /*
>>> > +            * Prevent users from writing negative or "no constraint" values
>>> > +            * directly.
>>> > +            */
>>> > +           if (value < 0 || value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
>>> > +                   return -EINVAL;
>
>>> > +           if (value == 0)
>>> > +                   value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
>>> > +   } else if (!strcmp(buf, "n/a") || !strcmp(buf, "n/a\n")) {
>>>
>>> Can the 2 checks for "n/a" be combined by checking first 3 characters?
>>
>> No, because "n/asomething" would then match too.
>
> If I don't missed anything, kernfs is aware of \n which means the
> first check is enough.
> Am I correct?

I'm not sure, honestly. :-)

Anyway, that can be fixed up later and the bug in question is rather urgent.

Thanks,
Rafael