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

From: Vinod Koul <vkoul@kernel.org>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
	tiwai@suse.de, broonie@kernel.org, gregkh@linuxfoundation.org,
	jank@cadence.com, srinivas.kandagatla@linaro.org,
	slawomir.blauciak@intel.com,
	Bard liao <yung-chuan.liao@linux.intel.com>,
	Rander Wang <rander.wang@linux.intel.com>,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Subject: Re: [PATCH 0/3] soundwire: use UniqueID only when relevant
Date: Sat, 9 Nov 2019 16:48:23 +0530	[thread overview]
Message-ID: <20191109111823.GD952516@vkoul-mobl> (raw)
In-Reply-To: <20191022234808.17432-1-pierre-louis.bossart@linux.intel.com>

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