linux-kernel - RE: [PATCH v3] Add driver to force WMI Thunderbolt controller power status

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Message-ID: <27f4070678744d0f80761a95579b4cd3@ausx13mpc120.AMER.DELL.COM>
Date:   Thu, 14 Sep 2017 06:42:03 +0000
From:   <Mario.Limonciello@...l.com>
To:     <lukas@...ner.de>
CC:     <dvhart@...radead.org>, <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <hughsient@...il.com>,
        <yehezkelshb@...il.com>, <mika.westerberg@...ux.intel.com>
Subject: RE: [PATCH v3] Add driver to force WMI Thunderbolt controller power
 status

> -----Original Message-----
> From: Lukas Wunner [mailto:lukas@...ner.de]
> Sent: Wednesday, September 13, 2017 12:20 PM
> To: Limonciello, Mario <Mario_Limonciello@...l.com>
> Cc: dvhart@...radead.org; LKML <linux-kernel@...r.kernel.org>; platform-driver-
> x86@...r.kernel.org; Richard Hughes <hughsient@...il.com>; Yehezkel Bernat
> <yehezkelshb@...il.com>; Mika Westerberg <mika.westerberg@...ux.intel.com>
> Subject: Re: [PATCH v3] Add driver to force WMI Thunderbolt controller power
> status
> 
> Sorry, late to the party.
> 
> On Fri, Sep 08, 2017 at 10:23:11AM -0500, Mario Limonciello wrote:
> > +	mode = hex_to_bin(buf[0]);
> > +	if (mode == 0 || mode == 1) {
> > +		status = wmi_evaluate_method(INTEL_WMI_THUNDERBOLT_GUID,
> 0, 1,
> > +					     &input, NULL);
> > +		if (ACPI_FAILURE(status)) {
> > +			pr_err("intel-wmi-thunderbolt: failed setting %s\n",
> > +			       buf);
> > +			return -ENODEV;
> > +		}
> > +	} else {
> > +		pr_err("intel-wmi-thunderbolt: unsupported mode: %d", mode);
> > +	}
> > +	return count;
> > +}
> 
> Seems odd to allow user space to fill the log by writing invalid data
> to sysfs, likewise that success is returned in the else case.
> I'd drop both pr_err() and return -EINVAL in the else case.
> 

Seems fine to me.  As Darren already queued the patch, I'll send a follow up patch 
to fix these two cases.

> 
> > +static const struct wmi_device_id intel_wmi_thunderbolt_id_table[] = {
> > +	{ .guid_string = INTEL_WMI_THUNDERBOLT_GUID },
> > +	{ },
> > +};
> 
> I'm not familiar with WMI, but don't you need a MODULE_DEVICE_TABLE here?
> How does user space know which module to load upon receiving the uevent?

Some macros for WMI bus devices.
https://github.com/torvalds/linux/blob/e0f25a3f2d052e36ff67a9b4db835c3e27e950d8/include/linux/wmi.h#L55
https://github.com/torvalds/linux/blob/master/include/linux/device.h#L1487