linux-kernel - Re: [PATCH v2 1/5] cpupower: Recognise amd-pstate active mode driver

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Message-ID: <ZJCQ2ypbQgZOOjt3@BLR-5CG13462PL.amd.com>
Date:   Mon, 19 Jun 2023 23:01:07 +0530
From:   Wyes Karny <wyes.karny@....com>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     trenn@...e.com, shuah@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, rafael@...nel.org,
        gautham.shenoy@....com, Ray.Huang@....com, Perry.Yuan@....com
Subject: Re: [PATCH v2 1/5] cpupower: Recognise amd-pstate active mode driver

Hi Mario,

On 18 Jun 20:58, Mario Limonciello wrote:
> On 6/16/23 07:06, Wyes Karny wrote:
> > amd-pstate active mode driver name is "amd-pstate-epp".  Add this to the
> > string matching condition to recognise amd-pstate active mode driver.
> > 
> > Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
> > Signed-off-by: Wyes Karny <wyes.karny@....com>
> > ---
> >   tools/power/cpupower/utils/helpers/misc.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/power/cpupower/utils/helpers/misc.c b/tools/power/cpupower/utils/helpers/misc.c
> > index 9547b29254a7..21f653cd472c 100644
> > --- a/tools/power/cpupower/utils/helpers/misc.c
> > +++ b/tools/power/cpupower/utils/helpers/misc.c
> > @@ -95,7 +95,7 @@ bool cpupower_amd_pstate_enabled(void)
> >   	if (!driver)
> >   		return ret;
> > -	if (!strcmp(driver, "amd-pstate"))
> > +	if (!strcmp(driver, "amd-pstate") || !strcmp(driver, "amd-pstate-epp"))
> 
> To avoid getting caught in the case that a kernel didn't have the patch
> separated from this series (for example if a distro missed it in a backport
> from separate directories), how about using strncmp() instead and just look
> for the prefix?

Sure, I'll update the patch.
I'm thinking of using strncmp(driver, "amd", 3), because in the above
case the epp driver would be "amd_pstate_epp" therefore common prefix is
only "amd".

Thanks,
Wyes
> 
> This would also let the tool be more future proofed in the case another
> amd-pstate driver was introduced later down the road as long as it stuck to
> "amd-pstate*"
> 
> >   		ret = true;
> >   	cpufreq_put_driver(driver);
>