From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Rosin <peda@axentia.se>
Subject: Re: Looking for guidance to support 74CBTLV3253 mux
Date: Fri, 11 Nov 2016 13:18:53 +0100
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To: MikeB <mabnhdev@gmail.com>
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On 2016-11-11 13:04, Peter Rosin wrote:
> On 2016-11-11 12:47, MikeB wrote:
>> On Thu, Nov 10, 2016 at 8:01 AM, Peter Rosin <peda@axentia.se> wrote:
>>>> There is however one requirement, the CPLD-mux must be "mux-locked"
>>>> as explained in Documentation/i2c/i2c-topology. Otherwise accesses
>>>> to devices behind that mux will lock the PCA9547 mux for the full
>>>> duration of the transaction and thus lock out any attempts to update
>>>> the CPLD mux as part of the transaction.
>>
>> Thank you for the informative reply.  I was unfamiliar with the new
>> mux and parent locking schemes.  They do make the solution for this
>> problem much easier to deal with.  I'm working with release 4.4
>> (Ubuntu Xenial), so the mux/parent locking hadn't shown up on my radar
>> yet.  Unfortunately, the target release for my work is and will remain
>> 4.4 for a while.
> 
> Lucky you :-)
> 
> Anyway, you might be able to backport the changes?
> 
> Start with:
> 
> a7ab72390b77062420fb50e4451f71c9321aae05
> "i2c: mux: add common data for every i2c-mux instance"
> 
> through to
> 
> 23fe440c59b9f08afe108e7ec7b6714cb2a3b955
> "i2c: mux: drop old unused i2c-mux api"
> 
> And then:
> 
> 785d32c7a9638a96730686663564d1842f7c2f03
> "i2c: allow adapter drivers to override the adapter locking"
> 
> through to
> 
> f76b724ee915415c52068c622ca48c652c1bd10c
> "i2c-mux: document i2c muxes and elaborate on parent-/mux-locked muxes"

Correction, those two commits became
8320f495cf441d593f7cd4f30e6b63455be71a2c and
2254d24aff3ab472dca287aef0123e8f0e06a14a when they got upstream.

> There are a handful of commits right after that that are also
> related, but they should be irrelevant to you...
> 
> Haven't tried it though, YMMV, and I might have forgotten a patch
> or two that came in later, but I don't remember any serious fallout...