linux-kernel - Re: [PATCH] i2c: i801: Register optional lis3lv02d i2c device on Dell machines

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Message-ID: <20170103092335.GB20337@pali>
Date:   Tue, 3 Jan 2017 10:23:35 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Michał Kępień <kernel@...pniu.pl>,
        Jean Delvare <jdelvare@...e.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Steven Honeyman <stevenhoneyman@...il.com>,
        Valdis.Kletnieks@...edu,
        Jochen Eisinger <jochen@...guin-breeder.org>,
        Gabriele Mazzotta <gabriele.mzt@...il.com>,
        Andy Lutomirski <luto@...nel.org>, Mario_Limonciello@...l.com,
        Alex Hung <alex.hung@...onical.com>,
        Takashi Iwai <tiwai@...e.de>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [PATCH] i2c: i801: Register optional lis3lv02d i2c device on
 Dell machines

On Tuesday 03 January 2017 10:06:41 Benjamin Tissoires wrote:
> On Dec 29 2016 or thereabouts, Pali Rohár wrote:
> > On Thursday 29 December 2016 22:09:32 Michał Kępień wrote:
> > > Also, just to make sure we do not overthink this, I understand that
> > > not every unit of the models from the whitelist has an
> > > accelerometer, correct?  In other words, could we perhaps skip the
> > > part where we are making sure the SMO88xx ACPI device is there?
> > 
> > Good question... At least for E6440 I'm did not thing it was possible to 
> > configure notebook without "3 axes free fall sensor".
> > 
> > But! In BIOS SETUP it is possible to disable free fall sensor. I will 
> > try to disable it there and will check what happen. My guess is that it 
> > will be disabled in ACPI.
> 
> Just adding my 2 cents regarding the whitelist and interaction between
> those 2 drivers. I find this very fragile to have only one available
> /dev/freefall node and to rely on the fairness of each driver to not bind
> one. It would have been much simpler to have /dev/freefallXX and a
> proper misc class device for it. This way, we don't even need to
> mutually exclude the drivers. But this is already 8 years old code, so I
> guess userspace expects this... (why isn't that using the input subsystem
> at all?).
> 
> Cheers,
> Benjamin.
> 

I think there is no problem with more /dev/freefall devices. With these
Dell drivers it should not happen as only one driver can request IRQ
which is associated with /dev/freefall. And /dev/freefal is registered
after acquiring IRQ.

But... there are other problems with it as wrote in previous emails.

-- 
Pali Rohár
pali.rohar@...il.com