linux-kernel - Re: [PATCH v2] input: mouse: add qci touchpad driver

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Date:	Fri, 13 Aug 2010 17:56:41 -0400
From:	Neil Leeder <nleeder@...eaurora.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Stepan Moskovchenko <stepanm@...eaurora.org>,
	linux-input@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Horace Fu <horace.fu@...ntatw.com>,
	Mandeep Singh Baines <msb@...omium.org>,
	Trilok Soni <tsoni@...eaurora.org>
Subject: Re: [PATCH v2] input: mouse: add qci touchpad driver

On 8/12/2010 10:49 PM, Dmitry Torokhov wrote:
> On Thu, Aug 12, 2010 at 01:58:18PM -0400, Neil Leeder wrote:
> Actually, since this is not a new touchpad but simply a PS/2 interface
> it should be implemented as a serio driver, not input device driver.
>
Dmitri,

Thanks for supplying that serio driver. I just have a couple of questions.

Even though the interface on the wpce775x EC happens to be a PS/2 
interface, this is completely hidden by the firmware on that device. To 
the linux driver it looks like a dedicated i2c connection directly to 
the touchpad. You can't substitute any other device on that PS/2 
interface without rewriting the firmware in the EC - it's not a generic 
interface.  A manufacturer could even move the touchpad from the PS/2 
interface to say GPIOs, re-write the firmware and the linux driver 
couldn't tell the difference. Does that change the rationale for using a 
serio driver?

If the request to use a serio driver is still valid, then it seems that 
the workqueue from the interrupt handler sends each byte of data 
received over i2c in a separate serio_interrupt() call to the touchpad 
driver. Touchpad data comes in 3-byte packets, so the touchpad driver 
will have to re-assemble the packet from 3 separate interrupts. Is that 
the intended use?

> Could you please tell me if the following works for you? Note that it
> expects IRQ to be set up properly (edge vs. level trigger) by the
> platform code

The i2c_board_info that supplies the irq # from platform code doesn't 
have a way to set i2c flags, and can't set_irq_type() until after 
irq_request(). This may require another platform_data struct to pass the 
trigger level in.

Thanks.

--
Neil
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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