Messages in this thread | | | Subject | Re: [alsa-devel] [PATCH] ACPI / device_sysfs: change _ADR representation to 64 bits | From | Pierre-Louis Bossart <> | Date | Tue, 30 Apr 2019 13:23:38 -0500 |
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On 4/16/19 3:09 AM, Rafael J. Wysocki wrote: > On Tue, Apr 16, 2019 at 5:29 AM Vinod Koul <vkoul@kernel.org> wrote: >> >> On 15-04-19, 10:18, Pierre-Louis Bossart wrote: >>> Standards such as the MIPI DisCo for SoundWire 1.0 specification >>> assume the _ADR field is 64 bits. >>> >>> _ADR is defined as an "Integer" represented as 64 bits since ACPI 2.0 >>> released in 2002. The low levels already use _ADR as 64 bits, e.g. in >>> struct acpi_device_info. >>> >>> This patch bumps the representation used for sysfs to 64 bits. >>> >>> Example with a SoundWire device, the results show the complete >>> vendorID and linkID which were omitted before: >>> >>> Before: >>> $ more /sys/bus/acpi/devices/device\:38/adr >>> 0x5d070000 >>> After: >>> $ more /sys/bus/acpi/devices/device\:38/adr >>> 0x000010025d070000 >> >> This looks fine but the sysfs file is an ABI. Not sure if we can modify >> the value returned this way.. Though it should not cause userspace >> reading 32bits to break... > > Well, IIRC using "08" instead of "016" in the format field would > preserve the existing behavior for 32-bit values, wouldn't it?
yes, but it makes the 64-bit address not aligned depending on the number of leading zeroes, see below. I get a migraine just looking at the results.
Maybe add a test to use 08 for values that are below 0xFFFFFFFF and 16 for addresses who really need the full range, typically because of an encoding?
w/ value-dependent format: /sys/bus/acpi/devices# cat */*/adr
0x00160000 0x00140003 0x000d0000 0x000d0002 0x000d0003 0x00070000 0x00070001 0x00070002 0x00070003 0x000010025d070100 0x000110025d070100 0x000210025d070100 0x000310025d070100 0x000010025d070000 0x000110025d070000 0x000210025d070000 0x000310025d070000 0x00000000
w/ 0x08 only:
0x00160000 0x00140003 0x000d0000 0x000d0002 0x000d0003 0x00070000 0x00070001 0x00070002 0x00070003 0x10025d070100 0x110025d070100 0x210025d070100 0x310025d070100 0x10025d070000 0x110025d070000 0x210025d070000 0x310025d070000 0x00000000 0x00000000
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