linux-kernel - Re: [PATCH v3 10/15] leds: leds-gpio: Add ACPI probing support

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Message-ID: <5364565.aEcZqpzdLW@wuerfel>
Date:	Wed, 01 Oct 2014 12:01:34 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	devicetree@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Aaron Lu <aaron.lu@...el.com>,
	Darren Hart <dvhart@...ux.intel.com>
Subject: Re: [PATCH v3 10/15] leds: leds-gpio: Add ACPI probing support

On Wednesday 01 October 2014 12:13:09 Mika Westerberg wrote:
> 
> > Regarding the MODULE_DEVICE_TABLE, I suspect the above won't work the
> > way you are hoping for, because once you get to dozens or hundreds of
> > drivers doing this, each device will show up with the same string,
> > so udev will try to load all the modules that list "PRP0001". That
> > doesn't look right. With the code from patch 3, you can probably drop
> > the acpi MODULE_DEVICE_TABLE() entirely and get the correct behavior.
> 
> It actually works like this now:
> 
>  # cd /sys/bus/platform/devices/PRP0001\:00/
>  DRIVER=leds-gpio
>  MODALIAS=of:Nprp0001TacpiCgpio-leds
> 
>  # cat modalias 
>  of:Nprp0001TacpiCgpio-leds
> 
> In other words the modalias changes to be of:Nprp0001Tacpi, e.g
> name=prp0001, type=acpi and then list of compatible values.
> 
> Udev then loads only module that matches the modalias so it should not
> load everything listing PRP0001 in their MODULE_DEVICE_TABLE().

I'm not completely following yet. I can see how this works now, but
how is this better than just using the existing modalias for OF?

	Arnd
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