linux-kernel - Re: [PATCH 2/6] platform/x86/intel/tpmi: Don't create devices for disabled features

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Date:   Thu, 30 Nov 2023 09:29:02 -0500
From:   srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Hans de Goede <hdegoede@...hat.com>, markgross@...nel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        platform-driver-x86@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] platform/x86/intel/tpmi: Don't create devices for
 disabled features

On Thu, 2023-11-30 at 14:26 +0200, Ilpo Järvinen wrote:
> On Tue, 28 Nov 2023, Srinivas Pandruvada wrote:
> 
> > If some TPMI features are disabled, don't create auxiliary devices.
> > In
> > this way feature drivers will not load.
> > 
> > While creating auxiliary devices, call tpmi_read_feature_status()
> > to
> > check feature state and return if the feature is disabled without
> > creating a device.
> > 
> > Signed-off-by: Srinivas Pandruvada
> > <srinivas.pandruvada@...ux.intel.com>
> > ---
> >  drivers/platform/x86/intel/tpmi.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/platform/x86/intel/tpmi.c
> > b/drivers/platform/x86/intel/tpmi.c
> > index c89aa4d14bea..4edaa182db04 100644
> > --- a/drivers/platform/x86/intel/tpmi.c
> > +++ b/drivers/platform/x86/intel/tpmi.c
> > @@ -604,9 +604,17 @@ static int tpmi_create_device(struct
> > intel_tpmi_info *tpmi_info,
> >         struct intel_vsec_device *vsec_dev = tpmi_info->vsec_dev;
> >         char feature_id_name[TPMI_FEATURE_NAME_LEN];
> >         struct intel_vsec_device *feature_vsec_dev;
> > +       struct tpmi_feature_state feature_state;
> >         struct resource *res, *tmp;
> >         const char *name;
> > -       int i;
> > +       int i, ret;
> > +
> > +       ret = tpmi_read_feature_status(tpmi_info, pfs-
> > >pfs_header.tpmi_id, &feature_state);
> > +       if (ret)
> > +               return ret;
> > +
> > +       if (!feature_state.enabled)
> > +               return -EOPNOTSUPP;
> 
> -ENODEV sounds more appropriate.  
The -EOPNOTSUPP is returned matching the next return statement, which
causes to continue to create devices which are supported and not
disabled. Any other error is real device creation will causes driver
modprobe to fail.

Thanks,
Srinivas