linux-kernel - Re: [PATCH v2 05/10] platform/x86: alienware-wmi-wmax: Improve platform profile probe

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Message-ID: <6f61f7dc-d5b8-7d61-c200-9c2c1ff2be7c@linux.intel.com>
Date: Tue, 4 Mar 2025 17:40:50 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Kurt Borja <kuurtb@...il.com>
cc: Armin Wolf <W_Armin@....de>, platform-driver-x86@...r.kernel.org, 
    Hans de Goede <hdegoede@...hat.com>, Dell.Client.Kernel@...l.com, 
    LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 05/10] platform/x86: alienware-wmi-wmax: Improve
 platform profile probe

On Tue, 25 Feb 2025, Kurt Borja wrote:

> Get and store the AWCC system description in alienware_awcc_setup()
> instead of awcc_platform_profile_probe() and add a check for integer
> overflows to avoid misbehaviors.
> 
> While at it, replace set_bit() with it's non-atomic version __set_bit()
> because `choices` belong to this thread only.
> 
> Signed-off-by: Kurt Borja <kuurtb@...il.com>
> Reviewed-by: Armin Wolf <W_Armin@....de>
> ---
>  .../platform/x86/dell/alienware-wmi-wmax.c    | 61 ++++++++++++++-----
>  1 file changed, 46 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/platform/x86/dell/alienware-wmi-wmax.c b/drivers/platform/x86/dell/alienware-wmi-wmax.c
> index 4a8335d90b5d..965b427f8f0a 100644
> --- a/drivers/platform/x86/dell/alienware-wmi-wmax.c
> +++ b/drivers/platform/x86/dell/alienware-wmi-wmax.c
> @@ -37,6 +37,9 @@
>  #define AWCC_THERMAL_MODE_MASK			GENMASK(3, 0)
>  #define AWCC_RESOURCE_ID_MASK			GENMASK(7, 0)
>  
> +/* Arbitrary limit based on supported models */
> +#define AWCC_MAX_RES_COUNT			16
> +
>  static bool force_platform_profile;
>  module_param_unsafe(force_platform_profile, bool, 0);
>  MODULE_PARM_DESC(force_platform_profile, "Forces auto-detecting thermal profiles without checking if WMI thermal backend is available");
> @@ -211,6 +214,17 @@ struct wmax_u32_args {
>  
>  struct awcc_priv {
>  	struct wmi_device *wdev;
> +	union {
> +		u32 system_description;
> +		struct {
> +			u8 fan_count;
> +			u8 temp_count;
> +			u8 unknown_count;
> +			u8 profile_count;
> +		} __packed;
> +		u8 res_count[4];
> +	} __packed;

I don't like it how __packed is now creeping its way into priv structure 
too. It doesn't even seem useful in this case as all those are naturally 
aligned and take 4 bytes, AFAICT. Why did you add it?

> +
>  	struct device *ppdev;
>  	u8 supported_profiles[PLATFORM_PROFILE_LAST];
>  };
> @@ -614,38 +628,41 @@ static int awcc_platform_profile_probe(void *drvdata, unsigned long *choices)
>  	enum platform_profile_option profile;
>  	struct awcc_priv *priv = drvdata;
>  	enum awcc_thermal_profile mode;
> -	u8 sys_desc[4];
> -	u32 first_mode;
> +	u8 id, offset = 0;
>  	u32 out_data;
>  	int ret;
> -	u8 id;
>  
> -	ret = awcc_thermal_information(priv->wdev, AWCC_OP_GET_SYSTEM_DESCRIPTION,
> -				       0, (u32 *) &sys_desc);
> -	if (ret < 0)
> -		return ret;
> -
> -	first_mode = sys_desc[0] + sys_desc[1];
> -
> -	for (u32 i = 0; i < sys_desc[3]; i++) {
> -		ret = awcc_op_get_resource_id(priv->wdev, i + first_mode, &out_data);
> +	/*
> +	 * Thermal profile IDs are listed last at offset
> +	 *	fan_count + temp_count + unknown_count
> +	 */
> +	for (unsigned int i = 0; i < ARRAY_SIZE(priv->res_count) - 1; i++)
> +		offset += priv->res_count[i];
>  
> +	for (unsigned int i = 0; i < priv->profile_count; i++) {
> +		ret = awcc_op_get_resource_id(priv->wdev, i + offset, &out_data);
>  		if (ret == -EIO)
>  			return ret;
>  
> +		/*
> +		 * Some devices report an incorrect number of thermal profiles
> +		 * so the resource ID list may end prematurely
> +		 */
>  		if (ret == -EBADRQC)
>  			break;
>  
>  		/* Some IDs have a BIT(8) flag that should be ignored */
>  		id = FIELD_GET(AWCC_RESOURCE_ID_MASK, out_data);
> -		if (!is_awcc_thermal_profile_id(id))
> +		if (!is_awcc_thermal_profile_id(id)) {
> +			dev_dbg(&priv->wdev->dev, "Unmapped thermal profile ID 0x%02x\n", id);
>  			continue;
> +		}
>  
>  		mode = FIELD_GET(AWCC_THERMAL_MODE_MASK, id);
>  		profile = awcc_mode_to_platform_profile[mode];
>  		priv->supported_profiles[profile] = id;
>  
> -		set_bit(profile, choices);
> +		__set_bit(profile, choices);
>  	}
>  
>  	if (bitmap_empty(choices, PLATFORM_PROFILE_LAST))
> @@ -655,7 +672,7 @@ static int awcc_platform_profile_probe(void *drvdata, unsigned long *choices)
>  		priv->supported_profiles[PLATFORM_PROFILE_PERFORMANCE] =
>  			AWCC_THERMAL_MODE_GMODE;
>  
> -		set_bit(PLATFORM_PROFILE_PERFORMANCE, choices);
> +		__set_bit(PLATFORM_PROFILE_PERFORMANCE, choices);
>  	}
>  
>  	return 0;
> @@ -686,6 +703,20 @@ static int alienware_awcc_setup(struct wmi_device *wdev)
>  	if (!priv)
>  		return -ENOMEM;
>  
> +	ret = awcc_thermal_information(wdev, AWCC_OP_GET_SYSTEM_DESCRIPTION,
> +				       0, &priv->system_description);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Sanity check */
> +	for (unsigned int i = 0; i < ARRAY_SIZE(priv->res_count); i++) {
> +		if (priv->res_count[i] > AWCC_MAX_RES_COUNT) {
> +			dev_err(&wdev->dev, "Malformed system description: 0x%08x\n",
> +				priv->system_description);
> +			return -ENXIO;
> +		}
> +	}
> +
>  	priv->wdev = wdev;
>  	dev_set_drvdata(&wdev->dev, priv);
>  
> 

-- 
 i.