On Sat, Oct 07, 2017 at 11:56:04AM +0000, mario.limoncie...@dell.com wrote:
> > -----Original Message-----
> > From: Greg KH [mailto:g...@kroah.com]
> > Sent: Saturday, October 7, 2017 1:54 AM
> > To: Limonciello, Mario <mario_limoncie...@dell.com>
> > Cc: dvh...@infradead.org; Andy Shevchenko <andy.shevche...@gmail.com>;
> > LKML <linux-kernel@vger.kernel.org>; platform-driver-...@vger.kernel.org;
> > Andy Lutomirski <l...@kernel.org>; quasi...@google.com;
> > pali.ro...@gmail.com; r...@rjwysocki.net; mj...@google.com; h...@lst.de
> > Subject: Re: [PATCH v5 08/14] platform/x86: dell-smbios: Add a sysfs 
> > interface for
> > SMBIOS tokens
> > 
> > On Fri, Oct 06, 2017 at 11:59:52PM -0500, Mario Limonciello wrote:
> > > Currently userspace tools can access system tokens via the dcdbas
> > > kernel module and a SMI call that will cause the platform to execute
> > > SMM code.
> > >
> > > With a goal in mind of deprecating the dcdbas kernel module a different
> > > method for accessing these tokens from userspace needs to be created.
> > >
> > > This is intentionally marked to only be readable as root as it can
> > > contain sensitive information about the platform's configuration.
> > >
> > > MAINTAINERS was missing for this driver.  Add myself and Pali to
> > > maintainers list for it.
> > >
> > > Signed-off-by: Mario Limonciello <mario.limoncie...@dell.com>
> > > ---
> > >  .../ABI/testing/sysfs-platform-dell-smbios         | 16 ++++++
> > >  MAINTAINERS                                        |  7 +++
> > >  drivers/platform/x86/dell-smbios.c                 | 64 
> > > ++++++++++++++++++++++
> > >  3 files changed, 87 insertions(+)
> > >  create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-smbios
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-platform-dell-smbios
> > b/Documentation/ABI/testing/sysfs-platform-dell-smbios
> > > new file mode 100644
> > > index 000000000000..d97f4bd5bd91
> > > --- /dev/null
> > > +++ b/Documentation/ABI/testing/sysfs-platform-dell-smbios
> > > @@ -0,0 +1,16 @@
> > > +What:            /sys/devices/platform/<platform>/tokens
> > > +Date:            November 2017
> > > +KernelVersion:   4.15
> > > +Contact: "Mario Limonciello" <mario.limoncie...@dell.com>
> > > +Description:
> > > +         A read-only description of Dell platform tokens
> > > +         available on the machine.
> > > +
> > > +         The tokens will be displayed in the following
> > > +         machine readable format with each token on a
> > > +         new line:
> > > +
> > > +         ID      Location        value
> > > +
> > > +         For example token:
> > > +         5       5       3
> > 
> > That's more than "one value per file" which is what sysfs requires, so
> > this isn't acceptable, sorry.
> 
> What's more acceptable to you to relay this information?  
> Binary sysfs attribute and export the structure format in a uapi?

binary sysfs apis are for passing "raw" data to/from firmware/hardware
to userspace, without the  kernel knowing anything about the structure
or format of the data.  Putting the format in a structure in a uapi
header kind of defeats that purpose :)

> or a collection of sysfs files?
> Eg:
> tokens/$x/id
> tokens/$x/location
> tokens/$s/value
> 
> I'm guessing the latter is the better way to go.

Good guess :)

thanks,

greg k-h

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