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Date: Mon, 18 Aug 2014 16:57:38 +0800
From: Hanjun Guo <hanjun.guo@...aro.org>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
CC: Darren Hart <dvhart@...ux.intel.com>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Aaron Lu <aaron.lu@...el.com>,
Max Eliaser <max.eliaser@...el.com>,
linux-acpi@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/9] ACPI: Add support for device specific properties
On 2014-8-18 16:27, Mika Westerberg wrote:
> On Mon, Aug 18, 2014 at 04:13:29PM +0800, Hanjun Guo wrote:
>> Hi,
>>
>> Some minor comments below.
>>
>> On 2014-8-17 14:04, Mika Westerberg wrote:
>>> 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 <dvhart@...ux.intel.com>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.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@...ux.intel.com>
>>> + * Darren Hart <dvhart@...ux.intel.com>
>>> + * Rafael J. Wysocki <rafael.j.wysocki@...el.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
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