linux-kernel - Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to power-up transition

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Message-ID: <Zh0qKeI-YPDE-NVT@hovoldconsulting.com>
Date: Mon, 15 Apr 2024 15:22:49 +0200
From: Johan Hovold <johan@...nel.org>
To: Kenny Levinsen <kl@...wtf>
Cc: lma@...omium.org, benjamin.tissoires@...hat.com, dianders@...omium.org,
	dtor@...omium.org, hdegoede@...hat.com, jikos@...nel.org,
	johan+linaro@...nel.org, kai.heng.feng@...onical.com,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	mripard@...nel.org, rad@...omium.org
Subject: Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to
 power-up transition

On Mon, Apr 15, 2024 at 12:28:28PM +0200, Kenny Levinsen wrote:
> > The problem is that the probe function calling i2c_smbus_read_byte()
> > is not aware that
> > uC on the other end is in a deep sleep state so the first read will
> > fail and so the whole probe.

> Well, the probe was just added to "avoid scary messages", so we could 
> just do away with it and fix the "scary messages" instead.

We also use it for devices that may not be populated (e.g. an optional
touchscreen) and in that case we should not print anything.

Johan