linux-kernel - Re: [PATCH] AMD_SFH: Add a DMI quirk entry for Chromebooks

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Date:   Wed, 13 Jul 2022 23:41:58 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Akihiko Odaki <akihiko.odaki@...il.com>
Cc:     Basavaraj Natikar <basavaraj.natikar@....com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] AMD_SFH: Add a DMI quirk entry for Chromebooks

On 7/10/22 03:15, Akihiko Odaki wrote:
> Google Chromebooks use Chrome OS Embedded Controller Sensor Hub instead
> of Sensor Hub Fusion and leaves MP2 uninitialized, which disables all
> functionalities, even including the registers necessary for feature
> detections.
> 
> The behavior was observed with Lenovo ThinkPad C13 Yoga.
> 

You missed that I suggested this from your earlier patch, you should add:

Suggested-by: Mario Limonciello <mario.limonciello@....com>

> Signed-off-by: Akihiko Odaki <akihiko.odaki@...il.com>
> ---
>   drivers/hid/amd-sfh-hid/amd_sfh_pcie.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
> index dadc491bbf6b..b91e1c95e543 100644
> --- a/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
> +++ b/drivers/hid/amd-sfh-hid/amd_sfh_pcie.c
> @@ -197,6 +197,18 @@ static const struct dmi_system_id dmi_sensor_mask_overrides[] = {
>   		},
>   		.driver_data = (void *)(ACEL_EN | MAGNO_EN),
>   	},
> +	{
> +		/*
> +		 * Google Chromebooks use Chrome OS Embedded Controller Sensor
> +		 * Hub instead of Sensor Hub Fusion and leaves MP2
> +		 * uninitialized, which disables all functionalities, even
> +		 * including the registers necessary for feature detections.
> +		 */
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "Google"),
> +		},
> +		.driver_data = (void *)0,
> +	},
>   	{ }
>   };
>   

Is this enough actually?  I would think you need to also modify 
amd_sfh_hid_client_init to special case the situation of "no sensors" 
and return -ENODEV otherwise it's going to try to read discovery status 
too and that might not be safe and deterministic.