linux-kernel - Re: [RFC PATCH] i2c: remove use of in

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Message-ID: <20190401112109.GB12232@hirez.programming.kicks-ass.net>
Date:   Mon, 1 Apr 2019 13:21:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-i2c@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Frederic Weisbecker <fweisbec@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH] i2c: remove use of in_atomic()

On Mon, Apr 01, 2019 at 01:13:24PM +0200, Wolfram Sang wrote:

> > Why must we allow i2c usage with IRQs disabled? Just say NO?
> 
> I'd love to. But quoting my patch description:
> 
> "This matches the use cases for atomic I2C transfers I have seen so far:
> very late communication (mostly to a PMIC) to powerdown or reboot the
> system."

Ah, sorry, I missed that.

> And yes, I would never recommend a HW design to use I2C for shutting
> down/rebooting. But such HW is out there.

Can we then make the whole thing conditional on:

  system_state > SYSTEM_RUNNING

Such that we're sure to never trigger this under any other conditions?