linux-kernel - Re: [PATCH] Input: goodix-berlin - Add sysfs interface for reading and writing touch IC registers

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Message-ID: <ZjrledLjn8RsGiwC@finisterre.sirena.org.uk>
Date: Wed, 8 May 2024 11:37:45 +0900
From: Mark Brown <broonie@...nel.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Jeff LaBundy <jeff@...undy.com>, Hans de Goede <hdegoede@...hat.com>,
	Charles Wang <charles.goodix@...il.com>, hadess@...ess.net,
	Richard Hughes <hughsient@...il.com>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, neil.armstrong@...aro.org
Subject: Re: [PATCH] Input: goodix-berlin - Add sysfs interface for reading
 and writing touch IC registers

On Tue, May 07, 2024 at 02:09:59PM -0700, Dmitry Torokhov wrote:
> On Tue, May 07, 2024 at 10:14:28AM -0500, Jeff LaBundy wrote:

> > For example, many devices must be placed in a bootloader mode during
> > the FW update, and may clamp or toggle an interrupt pin during this
> > mode switch. If user space initiates this sequence while the driver is
> > unaware of this process, it may attempt to read status registers from
> > an I2C address that is temporarily offline.

> And yet we have i2c-dev and hidraw that are often successfully used to
> flash the firmware, do diagnostics, etc. without encumbering the kernel.

Yeah, those seem like a reasonable enough model for safer devices - they
do the exclusion thing so you don't have a real driver running at the
same time.  For things like PMICs there's some concerns of course.

The other model I've seen used BTW is to expose a MTD device, if the
device actually looks like a MTD device (perhaps even is just a flash
that's fairly directly exposed) that minimises the kernel code quite
well.

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