linux-kernel - RE: [PATCH] Input: serio: make HYPERV_KEYBOARD depend on SERIO

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Message-ID: <EE124450C0AAF944A40DD71E61F878C9925D21@SINEX14MBXC417.southpacific.corp.microsoft.com>
Date:	Wed, 13 Aug 2014 05:24:35 +0000
From:	Dexuan Cui <decui@...rosoft.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Greg KH <gregkh@...uxfoundation.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	KY Srinivasan <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: RE: [PATCH] Input: serio: make HYPERV_KEYBOARD depend on
 SERIO_I8042=y

> -----Original Message-----
> From: Dmitry Torokhov
> Sent: Wednesday, August 13, 2014 1:55 AM
> > > > To decouple the dependency between the hyperv-keyboard and i8042
> > > > modules, I suppose we probably have to re-implement hyperv-
> keyboard by
> > > > using input_allocate_device(), input_register_device(), and using
> > > > input_report_key() to pass the key strokes to the high level.
> > >
> > > Yes, that would be the best thing to do,
> 
> Why? The backend still delivers AT keyboard data, so why does it make
> sense to write a new driver instead of making sure you can load
> atkbd/libps2 even without i8042 loaded?

Hi Dmitry,
Thanks for pointing this out!
I didn't realize input_report_key() can't accept AT keyboard scan codes.

> > The issue is: the latest Arch Linux release doesn't have a working (virtual)
> > keyboard when it runs as Generation 2 hyper-v guest -- when it runs as
> > a "traditional" Generation 1 hyper-v guest, everything works fine.
> > I hope this patch can temporarily help Arch users if they find the issue
> > and if they can rebuild the kernel.
> 
> The Arch users can simply select to build i8042 into the kernel as a
> workaround.
I agree.

> The proper solution is to allow loading libps2 module even if i8042 did
> not find its device. I wish I could simply drop this i8042_lock_chip and
> stuff, but unfortunately i8042 ports are not truly independent. We need
> to figure a way for libps2 to engage locking in i8042 if the driver is
> loaded, otherwise just ignore it.
> 
> Dmitry
Yeah, this seems the right solution.

How about this:
in libps2.c let's add  and export a function pointer
i8042_lock_chip_if_port_owner: it is used to replace the current 
	if (i8042_check_port_owner(ps2dev->serio))
		i8042_lock_chip();
The function pointer has a default value NULL, and in i8042.c: i8042_init()
we set the function pointer if an i8042 device is found?

Thanks,
-- Dexuan
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