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

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Date:   Wed, 4 Jan 2017 10:13:38 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Pali Rohár <pali.rohar@...il.com>,
        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
Subject: Re: [PATCH] i2c: i801: Register optional lis3lv02d i2c device on
 Dell machines

On Jan 03 2017 or thereabouts, Dmitry Torokhov wrote:
> On Tue, Jan 03, 2017 at 10:29:34PM +0100, Benjamin Tissoires wrote:
> > On Jan 03 2017 or thereabouts, Dmitry Torokhov wrote:
> >
> > > Yet another option: can we add a new flag to i2c_board_info controlling
> > > whether we want to enable/disable wiring up host notify interrupt?
> > 
> > That should be fairly easy to implement. For now, given that only Elan
> > and Synaptics are the one in need for Host Notify, it could be better to
> > request the Host Notify IRQ instead of disabling it unconditionally
> > (which would make the current yet 8 years old lis3lv02d driver happy
> > again).
> 
> I like that we have it done in i2c core instead of having drivers
> implementing it individually. Since you are saying that handling host
> notify is property of the slave/driver maybe we should be adding a flag
> to the *i2c_driver* structure to let i2c core that we want to have host
> notify mapped as interrupt if "native" interrupt is not supplied by the
> platform code?

I don't think this is a good idea. It's still a property of the I2C
device, not the driver. It's crappy under Windows, but that doesn't
prevent us to do the right thing.

I think the idea of having it at the i2c_board_info level is the good
one. It's a property of the device node and it wouldn't hurt me to have
a device tree property for that too (not entering the DT field now).
There is no ACPI prop for it too, but I wouldn't be surprised if it
comes in a later revision. The advantage of having it turned on
unconditionally is that we can instantiate it from userspace without
breaking the sysfs ABI.

Note that in the 2 uses I have seen so far of Host Notify, in both cases
I need to instantiate the I2C device from an other driver (psmouse) so I
can control the content of i2c_board_info.

Cheers,
Benjamin