On 2014-8-18 16:27, Mika Westerberg wrote:

On Mon, Aug 18, 2014 at 04:13:29PM +0800, Hanjun Guo wrote:

quoted

Hi,

Some minor comments below.

On 2014-8-17 14:04, Mika Westerberg wrote:

quoted

Device Tree is used in many embedded systems to describe the system
configuration to the OS. It supports attaching properties or name-value
pairs to the devices it describe. With these properties one can pass
additional information to the drivers that would not be available
otherwise.

ACPI is another configuration mechanism (among other things) typically
seen, but not limited to, x86 machines. ACPI allows passing arbitrary
data from methods but there has not been mechanism equivalent to Device
Tree until the introduction of _DSD in the recent publication of the
ACPI 5.1 specification.

In order to facilitate ACPI usage in systems where Device Tree is
typically used, it would be beneficial to standardize a way to retrieve
Device Tree style properties from ACPI devices, which is what we do in
this patch.

If a given device described in ACPI namespace wants to export properties it
must implement _DSD method (Device Specific Data, introduced with ACPI 5.1)
that returns the properties in a package of packages. For example:

	Name (_DSD, Package () {
		ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
		Package () {
			Package () {"name1", <VALUE1>},
			Package () {"name2", <VALUE2>},
			...
		}
	})

The UUID reserved for properties is daffd814-6eba-4d8c-8a91-bc9bbf4aa301
and is documented in the ACPI 5.1 companion document called "_DSD
Implementation Guide" [1], [2].

We add several helper functions that can be used to extract these
properties and convert them to different Linux data types.

The ultimate goal is that we only have one device property API that
retrieves the requested properties from Device Tree or from ACPI
transparent to the caller.

[1] http://www.uefi.org/sites/default/files/resources/_DSD-implementation-guide-toplevel.htm
[2] http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf

Signed-off-by: Darren Hart <redacted>
Signed-off-by: Rafael J. Wysocki <redacted>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/acpi/Makefile   |   1 +
 drivers/acpi/internal.h |   6 +
 drivers/acpi/property.c | 365 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/acpi/scan.c     |   2 +
 include/acpi/acpi_bus.h |   7 +
 include/linux/acpi.h    |  40 ++++++
 6 files changed, 421 insertions(+)
 create mode 100644 drivers/acpi/property.c

diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index ea55e0179f81..6e8269a111db 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile

@@ -45,6 +45,7 @@ acpi-y				+= acpi_pnp.o
 acpi-y				+= power.o
 acpi-y				+= event.o
 acpi-y				+= sysfs.o
+acpi-y				+= property.o
 acpi-$(CONFIG_X86)		+= acpi_cmos_rtc.o
 acpi-$(CONFIG_DEBUG_FS)		+= debugfs.o
 acpi-$(CONFIG_ACPI_NUMA)	+= numa.o

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 7de5b603f272..35001e2a8769 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h

@@ -178,4 +178,10 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev);
 bool acpi_osi_is_win8(void);
 #endif
 
+/*--------------------------------------------------------------------------
+				Device properties
+  -------------------------------------------------------------------------- */
+void acpi_init_properties(struct acpi_device *adev);
+void acpi_free_properties(struct acpi_device *adev);
+
 #endif /* _ACPI_INTERNAL_H_ */

diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
new file mode 100644
index 000000000000..093e834c35db
--- /dev/null
+++ b/drivers/acpi/property.c

@@ -0,0 +1,365 @@
+/*
+ * ACPI device specific properties support.
+ *
+ * Copyright (C) 2014, Intel Corporation
+ * All rights reserved.
+ *
+ * Authors: Mika Westerberg <mika.westerberg@linux.intel.com>
+ *          Darren Hart <dvhart@linux.intel.com>
+ *          Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/export.h>
+
+#include "internal.h"
+
+/* ACPI _DSD device properties UUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
+static const u8 prp_uuid[16] = {

s/prp_uuid/dsd_uuid ?

Well, it is actually the _DSD UUID that implements ACPI device
properties (hence the prp_) but I have no problems in changing that to
dsd_uuid instead.

Oh, I missed that part, since this UUID is only for ACPI device
properties, I agree with you that prp_ is better here.

Thanks
Hanjun