ACPI: property: Fix return value for nval == 0 in acpi_data_prop_read()

While analysing code for software and OF node for the corner case when
caller asks to read zero items in the supposed to be an array of values
I found that ACPI behaves differently to what OF does, i.e.

 1. It returns -EINVAL when caller asks to read zero items from integer
    array, while OF returns 0, if no other errors happened.

 2. It returns -EINVAL when caller asks to read zero items from string
    array, while OF returns -ENODATA, if no other errors happened.

Amend ACPI implementation to follow what OF does.

Fixes: b31384f ("Driver core: Unified device properties interface for platform firmware")
Signed-off-by: Andy Shevchenko <[email protected]>
Link: https://patch.msgid.link/[email protected]
[ rjw: Added empty line after a conditional ]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: andy-shev

drivers/acpi/property.c

@@ -1187,8 +1187,6 @@ static int acpi_data_prop_read(const struct acpi_device_data *data,
 		}
 		break;
 	}
-	if (nval == 0)
-		return -EINVAL;
 
 	if (obj->type == ACPI_TYPE_BUFFER) {
 		if (proptype != DEV_PROP_U8)
@@ -1212,9 +1210,11 @@ static int acpi_data_prop_read(const struct acpi_device_data *data,
 		ret = acpi_copy_property_array_uint(items, (u64 *)val, nval);
 		break;
 	case DEV_PROP_STRING:
-		ret = acpi_copy_property_array_string(
-			items, (char **)val,
-			min_t(u32, nval, obj->package.count));
+		nval = min_t(u32, nval, obj->package.count);
+		if (nval == 0)
+			return -ENODATA;
+
+		ret = acpi_copy_property_array_string(items, (char **)val, nval);
 		break;
 	default:
 		ret = -EINVAL;