linux-kernel - Re: [PATCH v2 6/9] Input: psmouse - add support for SMBus companions

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Message-ID: <20170320002204.GB27328@dtor-ws>
Date:   Sun, 19 Mar 2017 17:22:04 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Andrew Duggan <aduggan@...aptics.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v2 6/9] Input: psmouse - add support for SMBus companions

On Mon, Mar 13, 2017 at 12:01:59PM +0100, Benjamin Tissoires wrote:
> On Mar 10 2017 or thereabouts, Dmitry Torokhov wrote:
> > From: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > 
> > This provides glue between PS/2 devices that enumerate the RMI4 devices
> > and Elan touchpads to the RMI4 (or Elan) SMBus driver.
> > 
> > The SMBus devices keep their PS/2 connection alive. If the initialization
> > process goes too far (psmouse_activate called), the device disconnects
> > from the I2C bus and stays on the PS/2 bus, that is why we explicitly
> > disable PS/2 device reporting (by calling psmouse_deactivate) before
> > trying to register SMBus companion device.
> > 
> > The HID over I2C devices are enumerated through the ACPI DSDT, and
> > their PS/2 device also exports the InterTouch bit in the extended
> > capability 0x0C. However, the firmware keeps its I2C connection open
> > even after going further in the PS/2 initialization. We don't need
> > to take extra precautions with those device, especially because they
> > block their PS/2 communication when HID over I2C is used.
> > 
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > ---
> 
> Actually, one thing I noticed but forgot to say in my previous email:
> 
> If you call rescan from the sysfs, there is a chance the i2c device is
> still there while we are trying to reconnect the device. Which means
> that we fail at creating the i2c device, and then fall back on PS/2.
> 
> It's not a big issue, but still it will show some warning in the dmesg
> while attempting to create some sysfs files that already exist.
> 
> S solution could be to unlock the mutexes and wait for the termination
> of i2c_unregister_device, but I would believe the best approach would be
> to remove the mutexes in serio and psmouse, and directly call
> i2c_unregister_device in .disconnect.

Yeah, I think we'll have to live with rescan from sysfs hiccuping for
now. I want to do a bit of face-lift for serio/psmouse, but it will
take a bit of time.

Thanks.

-- 
Dmitry