linux-kernel - Re: [PATCH 2/2] platform/x86: Add Intel Software Defined Silicon driver

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Date:   Mon, 27 Sep 2021 19:36:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "David E. Box" <david.e.box@...ux.intel.com>
Cc:     lee.jones@...aro.org, hdegoede@...hat.com, mgross@...ux.intel.com,
        andriy.shevchenko@...ux.intel.com, srinivas.pandruvada@...el.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH 2/2] platform/x86: Add Intel Software Defined Silicon
 driver

On Mon, Sep 27, 2021 at 10:27:28AM -0700, David E. Box wrote:
> On Mon, 2021-09-27 at 06:04 +0200, Greg KH wrote:
> > On Sun, Sep 26, 2021 at 06:15:16PM -0700, David E. Box wrote:
> > > > > +static struct platform_driver sdsi_driver = {
> > > > > +       .driver = {
> > > > > +               .name           = SDSI_DEV_NAME,
> > > > > +               .dev_groups     = sdsi_groups,
> > > > > +       },
> > > > > +       .probe  = sdsi_probe,
> > > > > +       .remove = sdsi_remove,
> > > > > +};
> > > > > +module_platform_driver(sdsi_driver);
> > > > 
> > > > What causes the platform to know to register, and enable, this platform
> > > > driver?  Shouldn't there be some hardware involved that is discoverable
> > > > to enable it to load dynamically?
> > > 
> > > Ah. The patch that adds the SDSi platform device string was added to a series for the intel_pmt
> > > MFD
> > > driver and it's still waiting review. I see that complicates things. I can combine the two series
> > > together.
> > 
> > Do you have a pointer to the lore.kernel.org location of that series?
> 
> https://lore.kernel.org/all/20210922213007.2738388-1-david.e.box@linux.intel.com/
> 
> > 
> > Your code right here will bind to any system that it is loaded on, a
> > very dangerous thing...
> 
> It won't. It uses module alias to load against the SDSi specific MFD cell.

module aliases do not prevent someone from building the driver into
their kernel, or doing a simple 'modprobe'.  You need to bind your
driver to a real hardware resource (and reject it if it is not present),
otherwise this driver will break systems quite easily.

And again, why is this a platform driver and not just a "real" device on
a bus?  Heck, why not just use the auxiliary bus for stuff like this,
why are you craming pci attributes into the MFD subsystem?

thanks,

greg k-h