ACPI / scan: Add support for ACPI _CLS device matching

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. Also, certain classes of devices
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.

To support loadable module, current design uses _HID or _CID to match device's
modalias. With the new way of matching with _CLS this would requires modification
to the current ACPI modalias key to include _CLS. This patch appends PCI-defined
class-code to the existing ACPI modalias as following.

    acpi:<HID>:<CID1>:<CID2>:..:<CIDn>:<bbsspp>:
E.g:
    # cat /sys/devices/platform/AMDI0600:00/modalias
    acpi:AMDI0600:010601:

where bb is th base-class code, ss is te sub-class code, and pp is the
programming interface code

Since there would not be _HID/_CID in the ACPI matching table of the driver,
this patch adds a field to acpi_device_id to specify the matching _CLS.

    static const struct acpi_device_id ahci_acpi_match[] = {
        { ACPI_DEVICE_CLASS(PCI_CLASS_STORAGE_SATA_AHCI, 0xffffff) },
        {},
    };

In this case, the corresponded entry in modules.alias file would be:

    alias acpi*:010601:* ahci_platform

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 32 insertions, 2 deletions

diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
index eff7de1..e70fcd1 100644
--- a/scripts/mod/devicetable-offsets.c
+++ b/scripts/mod/devicetable-offsets.c
@@ -63,6 +63,8 @@ int main(void)
 
 	DEVID(acpi_device_id);
 	DEVID_FIELD(acpi_device_id, id);
+	DEVID_FIELD(acpi_device_id, cls);
+	DEVID_FIELD(acpi_device_id, cls_msk);
 
 	DEVID(pnp_device_id);
 	DEVID_FIELD(pnp_device_id, id);
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 84c86f3..5f20882 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -523,12 +523,40 @@ static int do_serio_entry(const char *filename,
 }
 ADD_TO_DEVTABLE("serio", serio_device_id, do_serio_entry);
 
-/* looks like: "acpi:ACPI0003 or acpi:PNP0C0B" or "acpi:LNXVIDEO" */
+/* looks like: "acpi:ACPI0003" or "acpi:PNP0C0B" or "acpi:LNXVIDEO" or
+ *             "acpi:bbsspp" (bb=base-class, ss=sub-class, pp=prog-if)
+ *
+ * NOTE: Each driver should use one of the following : _HID, _CIDs
+ *       or _CLS. Also, bb, ss, and pp can be substituted with ??
+ *       as don't care byte.
+ */
 static int do_acpi_entry(const char *filename,
 			void *symval, char *alias)
 {
 	DEF_FIELD_ADDR(symval, acpi_device_id, id);
-	sprintf(alias, "acpi*:%s:*", *id);
+	DEF_FIELD_ADDR(symval, acpi_device_id, cls);
+	DEF_FIELD_ADDR(symval, acpi_device_id, cls_msk);
+
+	if (id && strlen((const char *)*id))
+		sprintf(alias, "acpi*:%s:*", *id);
+	else if (cls) {
+		int i, byte_shift, cnt = 0;
+		unsigned int msk;
+
+		sprintf(&alias[cnt], "acpi*:");
+		cnt = 6;
+		for (i = 1; i <= 3; i++) {
+			byte_shift = 8 * (3-i);
+			msk = (*cls_msk >> byte_shift) & 0xFF;
+			if (msk)
+				sprintf(&alias[cnt], "%02x",
+					(*cls >> byte_shift) & 0xFF);
+			else
+				sprintf(&alias[cnt], "??");
+			cnt += 2;
+		}
+		sprintf(&alias[cnt], ":*");
+	}
 	return 1;
 }
 ADD_TO_DEVTABLE("acpi", acpi_device_id, do_acpi_entry);