linux-kernel - Re: [PATCH v2] ACPI / device_sysfs: change

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Date:   Thu, 2 May 2019 10:28:17 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        liam.r.girdwood@...ux.intel.com, jank@...ence.com, joe@...ches.com,
        srinivas.kandagatla@...aro.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Erik Schmauss <erik.schmauss@...el.com>,
        "open list:ACPI" <linux-acpi@...r.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@...ica.org>
Subject: Re: [PATCH v2] ACPI / device_sysfs: change _ADR representation to 64
 bits

On 01-05-19, 07:53, 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. 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@...ux.intel.com>
> ---
> 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)

Would prefer to use U32_MAX instead of 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

-- 
~Vinod