linux-kernel - Re: [PATCH v2 2/2] drm/privacy_screen_x86: Add entry for ChromeOS privacy-screen

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Date:   Mon, 20 Dec 2021 11:50:25 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Hans de Goede <hdegoede@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Benson Leung <bleung@...omium.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        gwendal@...gle.com, seanpaul@...gle.com, marcheau@...gle.com,
        rajatxjain@...il.com
Subject: Re: [PATCH v2 2/2] drm/privacy_screen_x86: Add entry for ChromeOS
 privacy-screen

On Fri, Dec 17, 2021 at 12:28:50PM -0800, Rajat Jain wrote:
> Add a static entry in the x86 table, to detect and wait for
> privacy-screen on some ChromeOS platforms.
> 
> Please note that this means that if CONFIG_CHROMEOS_PRIVACY_SCREEN is
> enabled, and if "GOOG0010" device is found in ACPI, then the i915 probe
> shall return EPROBE_DEFER until a platform driver actually registers the
> privacy-screen: https://hansdegoede.livejournal.com/25948.html
> 
> Signed-off-by: Rajat Jain <rajatja@...gle.com>
> ---
> v2: * Use #if instead of #elif
>     * Reorder the patches in the series.
>     * Rebased on drm-tip
> 
>  drivers/gpu/drm/drm_privacy_screen_x86.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_privacy_screen_x86.c b/drivers/gpu/drm/drm_privacy_screen_x86.c
> index a2cafb294ca6..0c5699ad70a3 100644
> --- a/drivers/gpu/drm/drm_privacy_screen_x86.c
> +++ b/drivers/gpu/drm/drm_privacy_screen_x86.c
> @@ -47,6 +47,18 @@ static bool __init detect_thinkpad_privacy_screen(void)
>  }
>  #endif
>  
> +#if IS_ENABLED(CONFIG_CHROMEOS_PRIVACY_SCREEN)
> +static bool __init detect_chromeos_privacy_screen(void)

Does marking this __init work in case there is a deferral? Can it happen
that privacy screen is a module and so will get loaded only after we
discarded __init sections.

> +{
> +	if (!acpi_dev_present("GOOG0010", NULL, -1))
> +		return false;
> +
> +	pr_info("%s: Need to wait for ChromeOS privacy-screen drvr", __func__);

I still do not see how this message is helpful. If it is really desired,
I'd put something into the code that calls into lookups.

> +	return true;
> +
> +}
> +#endif
> +
>  static const struct arch_init_data arch_init_data[] __initconst = {
>  #if IS_ENABLED(CONFIG_THINKPAD_ACPI)
>  	{
> @@ -58,6 +70,16 @@ static const struct arch_init_data arch_init_data[] __initconst = {
>  		.detect = detect_thinkpad_privacy_screen,
>  	},
>  #endif
> +#if IS_ENABLED(CONFIG_CHROMEOS_PRIVACY_SCREEN)
> +	{
> +		.lookup = {
> +			.dev_id = NULL,
> +			.con_id = NULL,
> +			.provider = "privacy_screen-GOOG0010:00",
> +		},
> +		.detect = detect_chromeos_privacy_screen,
> +	},
> +#endif
>  };
>  
>  void __init drm_privacy_screen_lookup_init(void)
> -- 
> 2.34.1.307.g9b7440fafd-goog
> 

Thanks.

-- 
Dmitry