linux-kernel - Re: [PATCH v3 3/3] drm/privacy_screen_x86: Add entry for ChromeOS privacy-screen

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Date:   Tue, 21 Dec 2021 19:53:28 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Rajat Jain <rajatja@...gle.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Benson Leung <bleung@...omium.org>,
        Henrique de Moraes Holschuh <hmh@....eng.br>,
        Mark Gross <markgross@...nel.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        ibm-acpi-devel@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org, gwendal@...gle.com,
        seanpaul@...gle.com, marcheu@...gle.com, dtor@...gle.com
Cc:     rajatxjain@...il.com
Subject: Re: [PATCH v3 3/3] drm/privacy_screen_x86: Add entry for ChromeOS
 privacy-screen

Hi,

On 12/20/21 23:28, 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>
> ---
> v3: * Remove the pr_info() from detect_chromeos_privacy_screen(), instead
>       enhance the one already present in drm_privacy_screen_lookup_init()
> v2: * Use #if instead of #elif
>     * Reorder the patches in the series.
>     * Rebased on drm-tip
> 
>  drivers/gpu/drm/drm_privacy_screen_x86.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_privacy_screen_x86.c b/drivers/gpu/drm/drm_privacy_screen_x86.c
> index a2cafb294ca6..0fdd2b500e6d 100644
> --- a/drivers/gpu/drm/drm_privacy_screen_x86.c
> +++ b/drivers/gpu/drm/drm_privacy_screen_x86.c
> @@ -47,6 +47,16 @@ static bool __init detect_thinkpad_privacy_screen(void)
>  }
>  #endif
>  
> +#if IS_ENABLED(CONFIG_CHROMEOS_PRIVACY_SCREEN)
> +static bool __init detect_chromeos_privacy_screen(void)
> +{
> +	if (!acpi_dev_present("GOOG0010", NULL, -1))
> +		return false;
> +
> +	return true;

This can be simplified to just:

	return acpi_dev_present("GOOG0010", NULL, -1);

> +}
> +#endif
> +
>  static const struct arch_init_data arch_init_data[] __initconst = {
>  #if IS_ENABLED(CONFIG_THINKPAD_ACPI)
>  	{
> @@ -58,6 +68,16 @@ 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)
> @@ -68,7 +88,8 @@ void __init drm_privacy_screen_lookup_init(void)
>  		if (!arch_init_data[i].detect())
>  			continue;
>  
> -		pr_info("Found '%s' privacy-screen provider\n",
> +		pr_info("Found '%s' privacy-screen provider."
> +			"Might have to defer probe for it...\n",
>  			arch_init_data[i].lookup.provider);

I'm afraid this change in the log message will only confuse users,
and for your goal of checking if a privacy-screen provider has
been detected, the original message is good enough.

Please drop this part of the patch.

Regards,

Hans



>  
>  		/* Make a copy because arch_init_data is __initconst */
>