linux-kernel - Re: [PATCH 0/3] soundwire: use UniqueID only when relevant

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Message-ID: <20191109111823.GD952516@vkoul-mobl>
Date:   Sat, 9 Nov 2019 16:48:23 +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,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>
Subject: Re: [PATCH 0/3] soundwire: use UniqueID only when relevant

On 22-10-19, 18:48, Pierre-Louis Bossart wrote:
> The hardware UniqueID, typically enabled with pin-strapping, is
> required during enumeration to avoid conflicts between devices of the
> same type.
> 
> When there are no devices of the same type, using the UniqueID is
> overkill and results in a lot of probe errors due to mismatches
> between ACPI tables and hardware capabilities. For example it's not
> uncommon for BIOS vendors to copy/paste the same settings between
> platforms but the hardware pin-strapping is different. This is
> perfectly legit and permitted by MIPI specs.
> 
> With this patchset, the UniqueID is only used when multiple devices of
> the same type are detected. The loop to detect multiple identical
> devices is not super efficient but with typically fewer than 4 devices
> per link there's no real incentive to be smarter.
> 
> This change is only implemented for ACPI platforms, for DeviceTree
> there is no change.

I do not fully agree with the approach here but I do understand why this
was done and do not have a better alternative, so applied now

-- 
~Vinod