linux-kernel - Re: [PATCH 4.16 269/272] pinctrl: msm: Use dynamic GPIO numbering

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Message-ID: <2898aafa-e185-8ad5-5f7f-9b81d4a36a8f@codeaurora.org>
Date:   Thu, 31 May 2018 10:09:50 -0500
From:   Timur Tabi <timur@...eaurora.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Sebastian Gottschall <s.gottschall@...wrt.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: Re: [PATCH 4.16 269/272] pinctrl: msm: Use dynamic GPIO numbering

On 5/31/18 7:12 AM, Greg Kroah-Hartman wrote:
> Why is it somehow ok for "future" kernels?  You can't break the api in
> the future for no reason.
> 
> So this needs to be the same everywhere.  If it is broken in 4.17-rc, it
> needs to be reverted.

This was discussed here:

https://www.spinics.net/lists/linux-arm-msm/msg32572.html

The code can't program the value to 0 *and* support multiple TLMM 
devices at the same time.  Prior to 4.18, it is not possible to support 
multiple TLMMs anyway, so blindly setting the base to -1 in the 4.17 
kernel just breaks existing user-space code that uses the legacy GPIO API.

(This patch in 4.18 is what provides support for multiple TLMMs: 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/pinctrl/qcom?id=f265e8b91bb50c7a732a171ddaeb0eef143bacd9)

So you can see in the thread that I proposed a compromise:

https://www.spinics.net/lists/linux-arm-msm/msg32596.html

but that was rejected

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