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    SubjectRE: [PATCH v6 14/14] platform/x86: dell-smbios-wmi: introduce userspace interface
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    > -----Original Message-----
    > From: Greg KH [mailto:greg@kroah.com]
    > Sent: Tuesday, October 10, 2017 8:59 AM
    > To: Limonciello, Mario <Mario_Limonciello@Dell.com>
    > Cc: dvhart@infradead.org; Andy Shevchenko <andy.shevchenko@gmail.com>;
    > LKML <linux-kernel@vger.kernel.org>; platform-driver-x86@vger.kernel.org;
    > Andy Lutomirski <luto@kernel.org>; quasisec@google.com;
    > pali.rohar@gmail.com; rjw@rjwysocki.net; mjg59@google.com; hch@lst.de
    > Subject: Re: [PATCH v6 14/14] platform/x86: dell-smbios-wmi: introduce
    > userspace interface
    >
    > On Mon, Oct 09, 2017 at 05:51:52PM -0500, Mario Limonciello wrote:
    > > + ret = device_create_file(&wdev->dev, &priv->req_buf_size_attr);
    > > + if (ret)
    > > + goto fail_create_sysfs;
    >
    > Why isn't the "WMI core" creating this sysfs file? Why have per-driver
    > sysfs files, making all of the different apis totally different? It's a
    > "common" attribute that they are all going to have to provide, right?
    >
    I hadn't really thought about that. I suppose it's entirely reasonable
    to have a way that all WMI ioctls for future drivers will advertise the size
    of their expected buffer the same way.

    So this does beg a question to others on this distribution who have worked
    on WMI drivers- do you know of any WM**/ methods with multiple instances
    that use different buffer sizes, or is it reasonable to expect that the buffer size
    is consistent between instances?

    Even in advanced MOF designs I haven't seen it, but this makes me
    wonder if an attribute should be created for every instance to be future proof.
    (For example $GUID/required_buffer_size/instance0,
    $GUID/required_buffer_size/instance1 etc)

    > That way you also don't race with userspace :)
    >
    > thanks,
    >
    > greg k-h

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