linux-kernel - Re: [PATCH] soundwire: debugfs: use controller id instead of link

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Message-ID: <57d5f1bd-50fa-30ab-03c0-260460e45d61@linaro.org>
Date:   Tue, 19 Jan 2021 17:17:59 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Vinod Koul <vkoul@...nel.org>
Cc:     alsa-devel@...a-project.org, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, sanyog.r.kale@...el.com,
        yung-chuan.liao@...ux.intel.com
Subject: Re: [PATCH] soundwire: debugfs: use controller id instead of link_id



On 19/01/2021 15:54, Pierre-Louis Bossart wrote:
> 
> 
> On 1/19/21 8:52 AM, Vinod Koul wrote:
>> On 15-01-21, 16:25, Srinivas Kandagatla wrote:
>>> link_id can be zero and if we have multiple controller instances
>>> in a system like Qualcomm debugfs will end-up with duplicate namespace
>>> resulting in incorrect debugfs entries.
>>>
>>> Using id should give a unique debugfs directory entry and should fix 
>>> below
>>> warning too.
>>> "debugfs: Directory 'master-0' with parent 'soundwire' already present!"
>>
>> Yeah id is guaranteed to be unique so this will work.
>>
>> Applied, thanks
> 
> This patch is a no-op for Intel, but I am not convinced it's the right 
> fix or the definitions are not consistent.

It depends if the intention is to represent full Hierarchy in debugfs, 
then I agree. Its was consistent even before!

currently we have
/sys/kernel/debug/soundwire/master-*

Are you suggesting that we have something like this:

/sys/kernel/debug/soundwire/xyz-controller/master-<LINK-ID> ??
/sys/kernel/debug/soundwire/xyz-controller/master-<LINK-ID>/xyz-slave/master-<LINK-ID> 
??


Or may be something much simpler like:

/sys/kernel/debug/soundwire/master-<ID>.<LINK_ID>


--srini

> 
>   * @link_id: Link id number, can be 0 to N, unique for each Master
>   * @id: bus system-wide unique id
> 
> In the MIPI/DisCo definitions, a controller can have multiple masters. 
> if you have multiple controllers, each of them should have their own 
> debugfs directory IMHO. It's totally fine to have multiple bus/masters 
> with a link_id == 0.