linux-kernel - Re: [PATCH V5 2/9] driver core: add ACPI based WBRF mechanism introduced by AMD

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Date:   Sat, 1 Jul 2023 02:51:22 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Evan Quan <evan.quan@....com>
Cc:     rafael@...nel.org, lenb@...nel.org, Alexander.Deucher@....com,
        Christian.Koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        Mario.Limonciello@....com, mdaenzer@...hat.com,
        maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de,
        hdegoede@...hat.com, jingyuwang_vip@....com, Lijo.Lazar@....com,
        jim.cromie@...il.com, bellosilicio@...il.com,
        andrealmeid@...lia.com, trix@...hat.com, jsg@....id.au,
        arnd@...db.de, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH V5 2/9] driver core: add ACPI based WBRF mechanism
 introduced by AMD

> +	argv4 = kzalloc(sizeof(*argv4) * (2 * num_of_ranges + 2 + 1), GFP_KERNEL);
> +	if (!argv4)
> +		return -ENOMEM;
> +
> +	argv4[arg_idx].package.type = ACPI_TYPE_PACKAGE;
> +	argv4[arg_idx].package.count = 2 + 2 * num_of_ranges;
> +	argv4[arg_idx++].package.elements = &argv4[1];
> +	argv4[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +	argv4[arg_idx++].integer.value = num_of_ranges;
> +	argv4[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +	argv4[arg_idx++].integer.value = action;

There is a lot of magic numbers in that kzalloc. It is being used as
an array, kcalloc() would be a good start to make it more readable.
Can some #define's be used to explain what the other numbers mean?

> +	/*
> +	 * Bit 0 indicates whether there's support for any functions other than
> +	 * function 0.
> +	 */

Please make use of the BIT macro to give the different bits
informative names.

> +	if ((mask & 0x1) && (mask & funcs) == funcs)
> +		return true;
> +
> +	return false;
> +}
> +

> +int acpi_amd_wbrf_retrieve_exclusions(struct device *dev,
> +				      struct wbrf_ranges_out *out)
> +{
> +	struct acpi_device *adev = ACPI_COMPANION(dev);
> +	union acpi_object *obj;
> +
> +	if (!adev)
> +		return -ENODEV;
> +
> +	obj = acpi_evaluate_wbrf(adev->handle,
> +				 WBRF_REVISION,
> +				 WBRF_RETRIEVE);
> +	if (!obj)
> +		return -EINVAL;
> +
> +	WARN(obj->buffer.length != sizeof(*out),
> +		"Unexpected buffer length");
> +	memcpy(out, obj->buffer.pointer, obj->buffer.length);

You WARN, and then overwrite whatever i passed the end of out?  Please
at least use min(obj->buffer.length, sizeof(*out)), but better still:

   if (obj->buffer.length != sizeof(*out)) {
         dev_err(dev, "BIOS FUBAR, ignoring wrong sized WBRT information");
	 return -EINVAL;
   }

> +#if defined(CONFIG_WBRF_GENERIC)
>  static struct exclusion_range_pool wbrf_pool;
>  
>  static int _wbrf_add_exclusion_ranges(struct wbrf_ranges_in *in)
> @@ -89,6 +92,7 @@ static int _wbrf_retrieve_exclusion_ranges(struct wbrf_ranges_out *out)
>  
>  	return 0;
>  }
> +#endif

I was expecting you would keep these tables, and then call into the
BIOS as well. Having this table in debugfs seems like a useful thing
to have for debugging the BIOS.

> +#ifdef CONFIG_WBRF_AMD_ACPI
> +#else
> +static inline bool
> +acpi_amd_wbrf_supported_consumer(struct device *dev) { return false; }
> +static inline bool
> +acpi_amd_wbrf_supported_producer(struct device *dev) {return false; }
> +static inline int
> +acpi_amd_wbrf_remove_exclusion(struct device *dev,
> +			       struct wbrf_ranges_in *in) { return -ENODEV; }
> +static inline int
> +acpi_amd_wbrf_add_exclusion(struct device *dev,
> +			    struct wbrf_ranges_in *in) { return -ENODEV; }
> +static inline int
> +acpi_amd_wbrf_retrieve_exclusions(struct device *dev,
> +				  struct wbrf_ranges_out *out) { return -ENODEV; }

Do you actually need these stub versions?

	Andrew