linux-kernel - Re: [PATCH v3 0/6] hid: Introduce device groups

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Message-ID: <20120503131904.GA11741@polaris.bitmath.org>
Date:	Thu, 3 May 2012 15:19:04 +0200
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Stephane Chatty <chatty@...c.fr>
Subject: Re: [PATCH v3 0/6] hid: Introduce device groups

> > 1) Add the devices in question back to the have_special_drivers list.
> 
> Well... The device presents valid mouse and keyboard interface that
> should be handled by hid-generic.
> The behavior of this particular device is the following:
> - when 1 finger is in use, then it sends events over the mouse interface
> - when 2 fingers are present, it sends events over the multitouch interface
> - when you physically trigger the switch mode button, a keyboard
> appears and it sends key events over the keyboard interface, and
> eventually mouse events if you press the "mouse" key.... ;-)
> 
> This crap is all inherited by the fact that Microsoft do not want to
> handle indirect touch, and the device maker found this solution to
> counter this.
> 
> To sum up, adding it to the have_special_drivers driver list won't
> work as we need part of the device to be handled by hid-generic.

So was this particular device never listed in have_special_drivers?

> > 2) Add the interface type to the group descision, which should
> > probably be done anyway. I have a patch in the pipe that, will send it
> > later today.
> 
> A simpler solution consists in adding the macros HID_USB_MT_DEVICE(v,
> p) and HID_BLUETOOTH_MT_DEVICE(v, p) as you had introduced in a
> earlier patch (I don't know why it disappeared).

No, the specific entries in the hid-multitouch device list matches any
group, so those defines were simplified away in the second version.

> The problem came out because:
> - hid-multitouch registered the triplet BUS_USB / VID / PID.
> - For each interface, it asks udev (or the kernel) which driver to
> use, and whatever .group was, it was always hid-multitouch that came
> out.
> 
> So it's just safer to specify the group for all multitouch devices.

This is still confusing. I thought the real problem was that the
non-mt interfaces do not match hid-generic. Solution 2) should take
care of that. What I don't understand is how those other interfaces
came to be handled by hid-generic before this patch, unless this
device was never listed in have_special_driver.

Are we talking about USB_DEVICE_ID_TOPSEED2_PERIPAD_701 here?

Henrik
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