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From: Vinod Koul <vkoul@kernel.org>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: alsa-devel@alsa-project.org, tiwai@suse.de,
	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
	broonie@kernel.org, srinivas.kandagatla@linaro.org,
	jank@cadence.com, slawomir.blauciak@intel.com,
	Bard liao <yung-chuan.liao@linux.intel.com>,
	Rander Wang <rander.wang@linux.intel.com>
Subject: Re: [alsa-devel] [PATCH 0/3] soundwire: use UniqueID only when relevant
Date: Sat, 9 Nov 2019 16:48:23 +0530
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
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Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 23:48 Pierre-Louis Bossart
2019-10-22 23:48 ` [alsa-devel] [PATCH 1/3] soundwire: remove bitfield for unique_id, use u8 Pierre-Louis Bossart
2019-10-24 11:29   ` Vinod Koul
2019-10-24 12:42     ` Pierre-Louis Bossart
2019-10-22 23:48 ` [alsa-devel] [PATCH 2/3] soundwire: slave: add helper to extract slave ID Pierre-Louis Bossart
2019-10-22 23:48 ` [alsa-devel] [PATCH 3/3] soundwire: ignore uniqueID when irrelevant Pierre-Louis Bossart
2019-10-24 11:39   ` Vinod Koul
2019-10-24 12:59     ` Pierre-Louis Bossart
2019-11-06 19:30 ` [alsa-devel] [PATCH 0/3] soundwire: use UniqueID only when relevant Pierre-Louis Bossart
2019-11-09 11:18 ` Vinod Koul [this message]

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