linux-kernel - Re: [PATCH V2] Input: synaptics-rmi4 - filter incomplete relative packet.

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Date:   Fri, 12 Aug 2022 12:28:18 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     margeyang <marge.yang@...aptics.corp-partner.google.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        hdegoede@...hat.com, benjamin.tissoires@...hat.com,
        marge.yang@...synaptics.com, derek.cheng@...synaptics.com,
        vincent.huang@...synaptics.com
Subject: Re: [PATCH V2] Input: synaptics-rmi4 - filter incomplete relative
 packet.

Hi Marge,

On Fri, Aug 12, 2022 at 04:43:25PM +0800, margeyang wrote:
> From: Marge Yang <marge.yang@...aptics.corp-partner.google.com>
> 
> RMI4 F03 supports the Stick function,
> it's designed to support relative packet.
> This patch supports the following case.
> When relative packet can't be reported completely,
> it may miss one byte or two byte.
> New Synaptics firmware will report PARITY error.
> When timeout error or parity error happens,
> RMI4 driver will sends 0xFE command and
> ask FW to Re-send stick packet again.

My understanding is that F03 is intended to be a pass-through mechanism
for PS/2-compatible devices. In that spirit all protocol handling and
validation should happen in psmouse driver that attaches to a serio port
provided by F03.

Historically we did not pay attention to parity and frame errors for
PS/2 mice/touchpads (and for keyboards on x86) but we coudl add such
code there. Do we actually observe this with RMI devices? Can RMI
firmware handle this better instead?

Thanks.

-- 
Dmitry