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

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Date:   Fri, 15 Sep 2017 09:44:39 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Mario.Limonciello@...l.com, dvhart@...radead.org,
        linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        hughsient@...il.com, yehezkelshb@...il.com
Subject: Re: [PATCH v3] Add driver to force WMI Thunderbolt controller power
 status

On Thu, Sep 14, 2017 at 05:59:19PM +0300, Mika Westerberg wrote:
> On Thu, Sep 14, 2017 at 02:52:27PM +0000, Mario.Limonciello@...l.com wrote:
> > > Looking at drivers/platform/x86/wmi.c:wmi_dev_uevent() it seems that
> > > a modalias consisting of "wmi:" followed by the GUID is sent to udevd.
> > > For udevd to then load the module, I suspect you need to add a
> > > MODULE_DEVICE_TABLE(wmi, ...) to your driver.
> > 
> > Ah, you're looking for this code from the WMI bus driver:
> > https://github.com/torvalds/linux/blob/master/drivers/platform/x86/wmi.c#L724
> > 
> > That happens when the bus is initialized.
> 
> That's right you get the uevent and whatnot but Lucas means that if you
> don't have MODULE_DEVICE_TABLE(wmi, ...) in the driver, udev cannot load
> the module automatically when the device appears.

Digging a bit deeper I notice the wmi drivers seem to solve this by
directly declaring a MODULE_ALIAS(), which is also present in Mario's
driver.  Mario, have you tested if auto-loading works if compiled as
a module?  If so, sorry for the noise.

Thanks,

Lukas