linux-kernel - Re: [PATCH v2 2/3] cpuidle:powernv: Add helper function to populate powernv idle states.

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Date:   Wed, 2 Nov 2016 08:03:01 +1100
From:   Paul Mackerras <paulus@...abs.org>
To:     Oliver O'Halloran <oohall@...il.com>
Cc:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Stewart Smith <stewart@...ux.vnet.ibm.com>,
        Balbir Singh <bsingharora@...il.com>,
        skiboot list <skiboot@...ts.ozlabs.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 2/3] cpuidle:powernv: Add helper function to populate
 powernv idle states.

On Tue, Nov 01, 2016 at 07:32:58PM +1100, Oliver O'Halloran wrote:
> On Thu, Oct 27, 2016 at 7:35 PM, Gautham R. Shenoy
> <ego@...ux.vnet.ibm.com> wrote:
> > From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> >
> > In the current code for powernv_add_idle_states, there is a lot of code
> > duplication while initializing an idle state in powernv_states table.
> >
> > Add an inline helper function to populate the powernv_states[] table for
> > a given idle state. Invoke this for populating the "Nap", "Fastsleep"
> > and the stop states in powernv_add_idle_states.
> >
> > Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> > ---
> >  drivers/cpuidle/cpuidle-powernv.c | 82 +++++++++++++++++++++++----------------
> >  include/linux/cpuidle.h           |  1 +
> >  2 files changed, 49 insertions(+), 34 deletions(-)
> >
> > diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> > index 7fe442c..11b22b9 100644
> > --- a/drivers/cpuidle/cpuidle-powernv.c
> > +++ b/drivers/cpuidle/cpuidle-powernv.c
> > @@ -167,6 +167,28 @@ static int powernv_cpuidle_driver_init(void)
> >         return 0;
> >  }
> >
> > +static inline void add_powernv_state(int index, const char *name,
> > +                                    unsigned int flags,
> > +                                    int (*idle_fn)(struct cpuidle_device *,
> > +                                                   struct cpuidle_driver *,
> > +                                                   int),
> > +                                    unsigned int target_residency,
> > +                                    unsigned int exit_latency,
> > +                                    u64 psscr_val)
> > +{
> > +       strncpy(powernv_states[index].name, name, CPUIDLE_NAME_LEN);
> > +       strncpy(powernv_states[index].desc, name, CPUIDLE_NAME_LEN);
> 
> If the supplied name is equal to CPUIDLE_NAME_LEN then strncpy() won't
> terminate the string. The least annoying fix is to memset() the whole
> structure to zero and set n to CPUIDLE_NAME_LEN - 1.

Or he could use strlcpy() instead of strncpy().

Paul.