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

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Message-ID: <caa9b0cb-ea85-e7de-6ada-35ad906dec28@linux.intel.com>
Date:   Wed, 6 Nov 2019 13:30:27 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     tiwai@...e.de, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        vkoul@...nel.org, broonie@...nel.org,
        srinivas.kandagatla@...aro.org, jank@...ence.com,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>
Subject: Re: [alsa-devel] [PATCH 0/3] soundwire: use UniqueID only when
 relevant



On 10/22/19 6:48 PM, 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.

Vinod, this series has been submitted for review on October 22 and I 
answered to your questions. There's been no feedback since October 24, 
so is there any sustained objection here?

ACPI platforms are completely unmanageable without this patchset.

> 
> Pierre-Louis Bossart (3):
>    soundwire: remove bitfield for unique_id, use u8
>    soundwire: slave: add helper to extract slave ID
>    soundwire: ignore uniqueID when irrelevant
> 
>   drivers/soundwire/bus.c       |  7 +--
>   drivers/soundwire/slave.c     | 98 +++++++++++++++++++++++++++--------
>   include/linux/soundwire/sdw.h |  4 +-
>   3 files changed, 84 insertions(+), 25 deletions(-)
>