RE: [PATCH v2] ACPI / device_sysfs: change _ADR representation to 64 bits

[Moore, Robert]

> -----Original Message-----
> From: Pierre-Louis Bossart [mailto:pierre-louis.bossart@xxxxxxxxxxxxxxx]
> Sent: Wednesday, May 1, 2019 5:53 AM
> To: alsa-devel@xxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; tiwai@xxxxxxx; broonie@xxxxxxxxxx;
> vkoul@xxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
> liam.r.girdwood@xxxxxxxxxxxxxxx; jank@xxxxxxxxxxx; joe@xxxxxxxxxxx;
> srinivas.kandagatla@xxxxxxxxxx; Pierre-Louis Bossart <pierre-
> louis.bossart@xxxxxxxxxxxxxxx>; Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>;
> Len Brown <lenb@xxxxxxxxxx>; Moore, Robert <robert.moore@xxxxxxxxx>;
> Schmauss, Erik <erik.schmauss@xxxxxxxxx>; open list:ACPI <linux-
> acpi@xxxxxxxxxxxxxxx>; open list:ACPI COMPONENT ARCHITECTURE (ACPICA)
> <devel@xxxxxxxxxx>
> Subject: [PATCH v2] ACPI / device_sysfs: change _ADR representation to
> 64 bits
> 
> 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.
> 
[Moore, Robert] 

Just to be precise: since acpi 2.0 the integer width is either 32 bits or 64 bits, depending on the version number of the DSDT (1-->32, 2 or greater --> 64).


> This patch bumps the representation used for sysfs to 64 bits. To avoid
> any compatibility/ABI issues, the printf format is only extended to 16
> characters when the actual _ADR value exceeds the 32 bit maximum.
> 
> 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
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-
> louis.bossart@xxxxxxxxxxxxxxx>
> ---
> v2: only use 64 bits when required to avoid compatibility issues
> (feedback from Vinod and Rafael)
> 
>  drivers/acpi/device_sysfs.c | 6 ++++--
>  include/acpi/acpi_bus.h     | 2 +-
>  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
> index 8940054d6250..7dda0ee05cd1 100644
> --- a/drivers/acpi/device_sysfs.c
> +++ b/drivers/acpi/device_sysfs.c
> @@ -428,8 +428,10 @@ static ssize_t acpi_device_adr_show(struct device
> *dev,  {
>  	struct acpi_device *acpi_dev = to_acpi_device(dev);
> 
> -	return sprintf(buf, "0x%08x\n",
> -		       (unsigned int)(acpi_dev->pnp.bus_address));
> +	if (acpi_dev->pnp.bus_address > 0xFFFFFFFF)
> +		return sprintf(buf, "0x%016llx\n", acpi_dev-
> >pnp.bus_address);
> +	else
> +		return sprintf(buf, "0x%08llx\n", acpi_dev->pnp.bus_address);
>  }
>  static DEVICE_ATTR(adr, 0444, acpi_device_adr_show, NULL);
> 
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h index
> f7981751ac77..9075e28ea60a 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -230,7 +230,7 @@ struct acpi_device_dir {
>  /* Plug and Play */
> 
>  typedef char acpi_bus_id[8];
> -typedef unsigned long acpi_bus_address;
> +typedef u64 acpi_bus_address;
>  typedef char acpi_device_name[40];
>  typedef char acpi_device_class[20];
> 
> --
> 2.17.1