linux-kernel - Re: [PATCH v3 05/18] mux: add mux_chip

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Date: Wed, 21 Feb 2024 11:59:05 +0100
From: Thomas Richard <thomas.richard@...tlin.com>
To: Andy Shevchenko <andy@...nel.org>
Cc: Linus Walleij <linus.walleij@...aro.org>,
 Bartosz Golaszewski <brgl@...ev.pl>, Tony Lindgren <tony@...mide.com>,
 Haojian Zhuang <haojian.zhuang@...aro.org>, Vignesh R <vigneshr@...com>,
 Aaro Koskinen <aaro.koskinen@....fi>,
 Janusz Krzysztofik <jmkrzyszt@...il.com>, Andi Shyti
 <andi.shyti@...nel.org>, Peter Rosin <peda@...ntia.se>,
 Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
 Philipp Zabel <p.zabel@...gutronix.de>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
 linux-i2c@...r.kernel.org, linux-phy@...ts.infradead.org,
 linux-pci@...r.kernel.org, gregory.clement@...tlin.com,
 theo.lebrun@...tlin.com, thomas.petazzoni@...tlin.com, u-kumar1@...com
Subject: Re: [PATCH v3 05/18] mux: add mux_chip_resume() function

On 2/16/24 16:07, Andy Shevchenko wrote:
> On Fri, Feb 16, 2024 at 08:52:17AM +0100, Thomas Richard wrote:
>> On 2/15/24 16:29, Andy Shevchenko wrote:
>>> On Thu, Feb 15, 2024 at 04:17:50PM +0100, Thomas Richard wrote:
> 
> ...
> 
>>>> +int mux_chip_resume(struct mux_chip *mux_chip)
>>>> +{
>>>> +	int global_ret = 0;
>>>> +	int ret, i;
>>>> +
>>>> +	for (i = 0; i < mux_chip->controllers; ++i) {
>>>> +		struct mux_control *mux = &mux_chip->mux[i];
>>>> +
>>>> +		if (mux->cached_state == MUX_CACHE_UNKNOWN)
>>>> +			continue;
>>>> +
>>>> +		ret = mux_control_set(mux, mux->cached_state);
>>>> +		if (ret < 0) {
>>>> +			dev_err(&mux_chip->dev, "unable to restore state\n");
>>>> +			if (!global_ret)
>>>> +				global_ret = ret;
>>>
>>> Hmm... This will record the first error and continue.
>>
>> In the v2 we talked about this with Peter Rosin.
>>
>> In fact, in the v1 (mux_chip_resume() didn't exists yet, everything was
>> done in the mmio driver) I had the same behavior: try to restore all
>> muxes and in case of error restore the first one.
>>
>> I don't know what is the right solution. I just restored the behavior I
>> had in v1.
> 
> Okay, I believe you know what you are doing, folks. But to me this approach
> sounds at bare minimum "unusual". Because the failures here are not fatal
> and recording the first one may or may not make sense and it's so fragile
> as it completely implementation-dependent.

I guess if there is an error, the resume is completely dead so no need
to continue.
If it's okay for Peter I can return on first failure.

Regards,

-- 
Thomas Richard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com