linux-kernel - Re: [PATCH] ACPI: property: Fix fwnode string properties matching

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Date:   Fri, 12 Feb 2021 12:32:09 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Calvin Johnson <calvin.johnson@....nxp.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH] ACPI: property: Fix fwnode string properties matching

On Thu, Feb 11, 2021 at 07:30:01PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Property matching does not work for ACPI fwnodes if the value of the
> given property is not represented as a package in the _DSD package
> containing it.  For example, the "compatible" property in the _DSD
> below
> 
>   Name (_DSD, Package () {
>     ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>     Package () {
>       Package () {"compatible", "ethernet-phy-ieee802.3-c45"}
>     }
>   })
> 
> will not be found by fwnode_property_match_string(), because the ACPI
> code handling device properties does not regard the single value as a
> "list" in that case.
> 
> Namely, fwnode_property_match_string() invoked to match a given
> string property value first calls fwnode_property_read_string_array()
> with the last two arguments equal to NULL and 0, respectively, in
> order to count the items in the value of the given property, with the
> assumption that this value may be an array.  For ACPI fwnodes, that
> operation is carried out by acpi_node_prop_read() which calls
> acpi_data_prop_read() for this purpose.  However, when the return
> (val) pointer is NULL, that function only looks for a property whose
> value is a package without checking the single-value case at all.
> 
> To fix that, make acpi_data_prop_read() check the single-value case
> regardless of the return pointer value if its return pointer argument
> is NULL and modify acpi_data_prop_read_single() handling that case to
> attempt to read the value of the property if the return pointer is
> NULL and return 1 if that succeeds.

Thanks, fine with me.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

I'll rebase the rest I have on to of this.

> Fixes: 3708184afc77 ("device property: Move FW type specific functionality to FW specific files")
> Reported-by: Calvin Johnson <calvin.johnson@....nxp.com>
> Cc: 4.13+ <stable@...r.kernel.org> # 4.13+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/property.c |   44 +++++++++++++++++++++++++++++++++-----------
>  1 file changed, 33 insertions(+), 11 deletions(-)
> 
> Index: linux-pm/drivers/acpi/property.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/property.c
> +++ linux-pm/drivers/acpi/property.c
> @@ -787,9 +787,6 @@ static int acpi_data_prop_read_single(co
>  	const union acpi_object *obj;
>  	int ret;
>  
> -	if (!val)
> -		return -EINVAL;
> -
>  	if (proptype >= DEV_PROP_U8 && proptype <= DEV_PROP_U64) {
>  		ret = acpi_data_get_property(data, propname, ACPI_TYPE_INTEGER, &obj);
>  		if (ret)
> @@ -799,28 +796,43 @@ static int acpi_data_prop_read_single(co
>  		case DEV_PROP_U8:
>  			if (obj->integer.value > U8_MAX)
>  				return -EOVERFLOW;
> -			*(u8 *)val = obj->integer.value;
> +
> +			if (val)
> +				*(u8 *)val = obj->integer.value;
> +
>  			break;
>  		case DEV_PROP_U16:
>  			if (obj->integer.value > U16_MAX)
>  				return -EOVERFLOW;
> -			*(u16 *)val = obj->integer.value;
> +
> +			if (val)
> +				*(u16 *)val = obj->integer.value;
> +
>  			break;
>  		case DEV_PROP_U32:
>  			if (obj->integer.value > U32_MAX)
>  				return -EOVERFLOW;
> -			*(u32 *)val = obj->integer.value;
> +
> +			if (val)
> +				*(u32 *)val = obj->integer.value;
> +
>  			break;
>  		default:
> -			*(u64 *)val = obj->integer.value;
> +			if (val)
> +				*(u64 *)val = obj->integer.value;
> +
>  			break;
>  		}
> +
> +		if (!val)
> +			return 1;
>  	} else if (proptype == DEV_PROP_STRING) {
>  		ret = acpi_data_get_property(data, propname, ACPI_TYPE_STRING, &obj);
>  		if (ret)
>  			return ret;
>  
> -		*(char **)val = obj->string.pointer;
> +		if (val)
> +			*(char **)val = obj->string.pointer;
>  
>  		return 1;
>  	} else {
> @@ -834,7 +846,7 @@ int acpi_dev_prop_read_single(struct acp
>  {
>  	int ret;
>  
> -	if (!adev)
> +	if (!adev || !val)
>  		return -EINVAL;
>  
>  	ret = acpi_data_prop_read_single(&adev->data, propname, proptype, val);
> @@ -928,10 +940,20 @@ static int acpi_data_prop_read(const str
>  	const union acpi_object *items;
>  	int ret;
>  
> -	if (val && nval == 1) {
> +	if (nval == 1 || !val) {
>  		ret = acpi_data_prop_read_single(data, propname, proptype, val);
> -		if (ret >= 0)
> +		/*
> +		 * The overflow error means that the property is there and it is
> +		 * single-value, but its type does not match, so return.
> +		 */
> +		if (ret >= 0 || ret == -EOVERFLOW)
>  			return ret;
> +
> +		/*
> +		 * Reading this property as a single-value one failed, but its
> +		 * value may still be represented as one-element array, so
> +		 * continue.
> +		 */
>  	}
>  
>  	ret = acpi_data_get_property_array(data, propname, ACPI_TYPE_ANY, &obj);
> 
> 
> 

-- 
With Best Regards,
Andy Shevchenko