linux-kernel - Re: [PATCH] soundwire: fix initializing sysfs for same devices on different buses

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Date:   Wed, 4 Oct 2023 09:57:49 -0400
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Takashi Iwai <tiwai@...e.de>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] soundwire: fix initializing sysfs for same devices on
 different buses



On 10/4/23 09:38, Greg Kroah-Hartman wrote:
> On Wed, Oct 04, 2023 at 09:16:47AM -0400, Pierre-Louis Bossart wrote:
>>
>>
>> On 10/4/23 09:02, Krzysztof Kozlowski wrote:
>>> If same devices with same device IDs are present on different soundwire
>>> buses, the probe fails due to conflicting device names and sysfs
>>> entries:
>>>
>>>   sysfs: cannot create duplicate filename '/bus/soundwire/devices/sdw:0:0217:0204:00:0'
>>>
>>> The link ID is 0 for both devices, so they should be differentiated by
>>> bus ID.  Add the bus ID so, the device names and sysfs entries look
>>> like:
>>
>> I am pretty sure this will break Intel platforms by changing the device
>> names.
>>
>> sof_sdw.c:      else if (is_unique_device(adr_link, sdw_version, mfg_id,
>> part_id,
>> sof_sdw.c:
>> "sdw:%01x:%04x:%04x:%02x", link_id,
>> sof_sdw.c:
>> "sdw:%01x:%04x:%04x:%02x:%01x", link_id,
> 
> device id name changes shouldn't break things, what is requring them to
> look a specific way?

it's the ASoC dailink creation that relies on strings, we have similar
cases for I2C.

There's no requirement that the name follows any specific convention,
just that when you want to rely on a specific device for an ASoC card
you need to use the string that matches its device name.

I am not sure how we would modify the Intel machine driver though
because the bus ID is IDA-based, so there's no way to predict what it
might be.