linux-kernel - Re: [PATCH 3/3] soundwire: bus_type: add sdw_master

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Date:   Tue, 12 May 2020 09:36:25 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     alsa-devel@...a-project.org, tiwai@...e.de,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        ranjani.sridharan@...ux.intel.com, hui.wang@...onical.com,
        broonie@...nel.org, srinivas.kandagatla@...aro.org,
        jank@...ence.com, mengdong.lin@...el.com,
        slawomir.blauciak@...el.com, sanyog.r.kale@...el.com,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        rander.wang@...ux.intel.com, bard.liao@...el.com
Subject: Re: [PATCH 3/3] soundwire: bus_type: add sdw_master_device support



On 5/11/20 10:30 PM, Vinod Koul wrote:
> On 11-05-20, 14:00, Pierre-Louis Bossart wrote:
>>>> +	md = &bus->md;
>>>> +	md->dev.bus = &sdw_bus_type;
>>>> +	md->dev.type = &sdw_master_type;
>>>> +	md->dev.parent = parent;
>>>> +	md->dev.of_node = parent->of_node;
>>>> +	md->dev.fwnode = fwnode;
>>>> +	md->dev.dma_mask = parent->dma_mask;
>>>> +
>>>> +	dev_set_name(&md->dev, "sdw-master-%d", bus->link_id);
>>>
>>> This give nice sdw-master-0. In DT this comes from reg property. I dont
>>> seem to recall if the ACPI/Disco spec treats link_id as unique across
>>> the system, can you check that please, if not we would need to update
>>> this.
>> Table 3 in the Disco for Soundwire 1.0 spec: "all LinkID values are relative
>> to the immediate parent Device."
>>
>> There isn't any known implementation with more than one controller.
> 
> But then it can come in "future" right. So lets try to make it future
> proof by not using the link_id (we can expose that as a sysfs if people
> want to know). So a global unique id needs to allocated (hint: idr or
> equivalent) and used as master_id

Can you clarify if you are asking for a global ID for Intel/ACPI 
platforms, or for DT as well? I can't figure out from the 
soundwire-controller.yaml definitions if there is already a notion of 
unique ID.

properties:
   $nodename:
     pattern: "^soundwire(@.*)?$"

    soundwire@...0000 {
         #address-cells = <2>;
         #size-cells = <0>;
         reg = <0x0c2d0000 0x2000>;