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Date:   Mon, 31 Jan 2022 13:13:18 +0200
From:   Heikki Krogerus <heikki.krogerus@linux.intel.com>
To:     Prashant Malani <pmalani@chromium.org>
Cc:     linux-kernel@vger.kernel.org, Alyssa Ross <hi@alyssa.is>,
        Tzung-Bi Shih <tzungbi@google.com>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.org>
Subject: Re: [PATCH v2] platform/chrome: cros_ec_typec: Check for EC device
Message-ID: <YffETvxepY2uU/qT@kuha.fi.intel.com>
References: <20220126190219.3095419-1-pmalani@chromium.org>
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On Wed, Jan 26, 2022 at 07:02:20PM +0000, Prashant Malani wrote:
> The Type C ACPI device on older Chromebooks is not generated correctly
> (since their EC firmware doesn't support the new commands required). In
> such cases, the crafted ACPI device doesn't have an EC parent, and it is
> therefore not useful (it shouldn't be generated in the first place since
> the EC firmware doesn't support any of the Type C commands).
> 
> To handle devices which use these older firmware revisions, check for
> the parent EC device handle, and fail the probe if it's not found.
> 
> Fixes: fdc6b21e2444 ("platform/chrome: Add Type C connector class driver")
> Reported-by: Alyssa Ross <hi@alyssa.is>
> Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
> Signed-off-by: Prashant Malani <pmalani@chromium.org>

FWIW:

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Hi Alyssa, could you kindly test this with your existing setup? Thanks!
> 
> Changes in v2:
> - Added newlines as suggested by reviewers.
> - Added Reviewed-by tag from Tzung-Bi.
> 
>  drivers/platform/chrome/cros_ec_typec.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index 5de0bfb0bc4d..952c1756f59e 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -1075,7 +1075,13 @@ static int cros_typec_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	typec->dev = dev;
> +
>  	typec->ec = dev_get_drvdata(pdev->dev.parent);
> +	if (!typec->ec) {
> +		dev_err(dev, "couldn't find parent EC device\n");
> +		return -ENODEV;
> +	}
> +
>  	platform_set_drvdata(pdev, typec);
>  
>  	ret = cros_typec_get_cmd_version(typec);
> -- 
> 2.35.0.rc0.227.g00780c9af4-goog

-- 
heikki