linux-kernel - Re: [PATCH 01/10] i2c: add suspended flag and accessors for i2c adapters

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Message-ID: <c1518533-ccc0-1a82-31b4-959682fb9b9e@axentia.se>
Date:   Fri, 21 Dec 2018 18:40:08 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Wolfram Sang <wsa@...-dreams.de>,
        Hans de Goede <hdegoede@...hat.com>
CC:     Lukas Wunner <lukas@...ner.de>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/10] i2c: add suspended flag and accessors for i2c
 adapters

On 2018-12-21 15:50, Wolfram Sang wrote:
> 
>>>> I think this might be as simple as adding:
>>>>
>>>> 	if (WARN_ON(adap->dev.parent->power.is_suspended))
>>>> 		return -ESHUTDOWN;
> 
> Peter, I think this should work for muxes, too, or? The i2c_transfer()
> call to the mux will not be rejected, but it will be later when we reach
> the root adapter. And then the error code will be pushed down the tree
> until we arrive at the mux again. So, the rejection will not happen at
> the earliest time, but it will happen. Is my understanding correct?

Yes, I agree with that analysis. All mux actions eventually end up with
an __i2c_transfer() call on the relevant root adapter. Hmm, but not *all*
calls. How about SMBus adapters? Should there not be a similar WARN_ON
in __i2c_smbus_xfer?

But maybe that's not applicable for some reason? Just asking...

Cheers,
Peter