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

[Mika Westerberg]

On Thu, Feb 11, 2021 at 07:30:01PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> 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.
> 
> Fixes: 3708184afc77 ("device property: Move FW type specific functionality to FW specific files")
> Reported-by: Calvin Johnson <calvin.johnson@xxxxxxxxxxx>
> Cc: 4.13+ <stable@xxxxxxxxxxxxxxx> # 4.13+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>