linux-kernel - Re: [PATCH] platform/x86: ideapad-laptop: Add has_touchpad

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Message-ID: <XVSpzJf9TdCi-rg53vfxB7yLg8VJQsQVbqoC1Fu1L7tL5mPKCpMABkedQNatITMiUy7pvBC7g0Cqd30-zqc0bCsSSoy5YXp_gJLTLM0odTg=@protonmail.com>
Date:   Fri, 01 Jan 2021 17:09:37 +0000
From:   Barnabás Pőcze <pobrn@...tonmail.com>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Ike Panhc <ike.pan@...onical.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: ideapad-laptop: Add has_touchpad_switch

Hi

2021. január 1., péntek 17:08 keltezéssel, Jiaxun Yang írta:

> [...]
> > > @@ -1006,6 +1018,10 @@ static int ideapad_acpi_add(struct platform_device *pdev)
> > >  	if (!priv->has_hw_rfkill_switch)
> > >  		write_ec_cmd(priv->adev->handle, VPCCMD_W_RF, 1);
> > >
> > > +	/* The same for Touchpad */
> > > +	if (!priv->has_touchpad_switch)
> > > +		write_ec_cmd(priv->adev->handle, VPCCMD_W_TOUCHPAD, 1);
> > > +
> >
> > Shouldn't it be the other way around: `if (priv->has_touchpad_switch)`?
>
> It is to prevent accidentally disable touchpad on machines that do have EC switch,
> so it's intentional.
> [...]

Sorry, but the explanation not fully clear to me. The commit message seems to
indicate that some models "do not use EC to switch touchpad", and I take that
means that reading from VPCCMD_R_TOUCHPAD will not reflect the actual state of the
touchpad and writing to VPCCMD_W_TOUCHPAD will not change the state of the touchpad.

But then why do you still write to VPCCMD_W_TOUCHPAD on devices where supposedly
this does not have any effect (at least not the desired one)? And the part of the
code I made my comment about only runs on machines on which the touchpad supposedly
cannot be controlled by the EC. What am I missing?

And there is the other problem: on some machines, this patch removes working
functionality.

Regards,
Barnabás Pőcze