[V3 PATCH 1/2] ACPI / scan: Add support for ACPI _CLS device matching

[Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>]

Device drivers typically use ACPI _HIDs/_CIDs listed in struct device_driver
acpi_match_table to match devices. However, for generic drivers, we do
not want to list _HID for all supported devices, and some device classes
do not have _CID (e.g. SATA, USB). Instead, we can leverage ACPI _CLS,
which specifies PCI-defined class code (i.e. base-class, subclass and
programming interface).

This patch adds support for matching ACPI devices using the _CLS method.

Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
---
 drivers/acpi/scan.c             | 75 +++++++++++++++++++++++++++++++++++++++--
 include/acpi/acnames.h          |  1 +
 include/linux/acpi.h            | 10 ++++++
 include/linux/device.h          |  1 +
 include/linux/mod_devicetable.h |  6 ++++
 5 files changed, 90 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index dc4d896..0579395 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -987,13 +987,82 @@ static bool acpi_of_driver_match_device(struct device *dev,
 bool acpi_driver_match_device(struct device *dev,
 			      const struct device_driver *drv)
 {
-	if (!drv->acpi_match_table)
-		return acpi_of_driver_match_device(dev, drv);
+	bool ret = false;
 
-	return !!acpi_match_device(drv->acpi_match_table, dev);
+	if (drv->acpi_match_table)
+		ret = !!acpi_match_device(drv->acpi_match_table, dev);
+
+	/* Next, try to match with special "PRP0001" _HID */
+	if (!ret && drv->of_match_table)
+		ret = acpi_of_driver_match_device(dev, drv);
+
+	/* Next, try to match with PCI-defined class-code */
+	if (!ret && drv->acpi_match_cls)
+		ret = acpi_match_device_cls(drv->acpi_match_cls, dev);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(acpi_driver_match_device);
 
+/**
+ * acpi_match_device_cls - Match a struct device against a ACPI _CLS method
+ * @dev_cls: A pointer to struct acpi_device_cls object to match against.
+ * @dev: The ACPI device structure to match.
+ *
+ * Check if @dev has a valid ACPI and _CLS handle. If there is a
+ * struct acpi_device_cls object for that handle, use that object to match
+ * against the given struct acpi_device_cls object.
+ *
+ * Return true on success or false on failure.
+ */
+bool acpi_match_device_cls(const struct acpi_device_cls *dev_cls,
+			  const struct device *dev)
+{
+	acpi_status status;
+	union acpi_object *pkg;
+	struct acpi_device_cls cls;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	struct acpi_buffer format = { sizeof("NNN"), "NNN" };
+	struct acpi_buffer state = { 0, NULL };
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+
+	if (!adev || !adev->status.present || !dev_cls)
+		return false;
+
+	status = acpi_evaluate_object(adev->handle, METHOD_NAME__CLS,
+				      NULL, &buffer);
+	if (ACPI_FAILURE(status))
+		return false;
+
+	/**
+	 * Note:
+	 * ACPIv5.1 defines the package to contain 3 integers for
+	 * Base-Class code, Sub-Class code, and Programming Interface code.
+	 */
+	pkg = buffer.pointer;
+	if (!pkg ||
+	    (pkg->type != ACPI_TYPE_PACKAGE) ||
+	    (pkg->package.count != 3)) {
+		dev_dbg(&adev->dev, "Invalid _CLS data\n");
+		goto out;
+	}
+
+	state.length = sizeof(struct acpi_device_cls);
+	state.pointer = &cls;
+
+	status = acpi_extract_package(pkg, &format, &state);
+	if (ACPI_FAILURE(status))
+		goto out;
+
+	return (dev_cls->base_class == cls.base_class &&
+		dev_cls->sub_class == cls.sub_class &&
+		dev_cls->prog_interface == cls.prog_interface);
+out:
+	kfree(pkg);
+	return false;
+}
+EXPORT_SYMBOL_GPL(acpi_match_device_cls);
+
 static void acpi_free_power_resources_lists(struct acpi_device *device)
 {
 	int i;
diff --git a/include/acpi/acnames.h b/include/acpi/acnames.h
index 7461327..22332a6 100644
--- a/include/acpi/acnames.h
+++ b/include/acpi/acnames.h
@@ -51,6 +51,7 @@
 #define METHOD_NAME__BBN        "_BBN"
 #define METHOD_NAME__CBA        "_CBA"
 #define METHOD_NAME__CID        "_CID"
+#define METHOD_NAME__CLS        "_CLS"
 #define METHOD_NAME__CRS        "_CRS"
 #define METHOD_NAME__DDN        "_DDN"
 #define METHOD_NAME__HID        "_HID"
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 536991b..9a01d5d 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -442,6 +442,10 @@ const struct acpi_device_id *acpi_match_device(const struct acpi_device_id *ids,
 
 extern bool acpi_driver_match_device(struct device *dev,
 				     const struct device_driver *drv);
+
+bool acpi_match_device_cls(const struct acpi_device_cls *dev_cls,
+			   const struct device *dev);
+
 int acpi_device_uevent_modalias(struct device *, struct kobj_uevent_env *);
 int acpi_device_modalias(struct device *, char *, int);
 void acpi_walk_dep_device_list(acpi_handle handle);
@@ -542,6 +546,12 @@ static inline const struct acpi_device_id *acpi_match_device(
 	return NULL;
 }
 
+static inline bool acpi_match_device_cls(const struct acpi_device_cls *dev_cls,
+					 const struct device *dev)
+{
+	return false;
+}
+
 static inline bool acpi_driver_match_device(struct device *dev,
 					    const struct device_driver *drv)
 {
diff --git a/include/linux/device.h b/include/linux/device.h
index fb50673..8e259c5c 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -237,6 +237,7 @@ struct device_driver {
 
 	const struct of_device_id	*of_match_table;
 	const struct acpi_device_id	*acpi_match_table;
+	const struct acpi_device_cls	*acpi_match_cls;
 
 	int (*probe) (struct device *dev);
 	int (*remove) (struct device *dev);
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 745def8..cf0e0d198 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -191,6 +191,12 @@ struct acpi_device_id {
 	kernel_ulong_t driver_data;
 };
 
+struct acpi_device_cls {
+	kernel_ulong_t base_class;
+	kernel_ulong_t sub_class;
+	kernel_ulong_t prog_interface;
+};
+
 #define PNP_ID_LEN	8
 #define PNP_MAX_DEVICES	8
 
-- 
2.1.0