linux-kernel - Re: [PATCH v13 03/10] mux: minimal mux subsystem and gpio-based mux controller

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Message-ID: <9e3d48c4-0dbc-3e80-c653-b0357abf1d6f@axentia.se>
Date:   Fri, 21 Apr 2017 16:32:20 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Philipp Zabel <p.zabel@...gutronix.de>
CC:     <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Jonathan Corbet <corbet@....net>, <linux-i2c@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <linux-doc@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        <kernel@...gutronix.de>
Subject: Re: [PATCH v13 03/10] mux: minimal mux subsystem and gpio-based mux
 controller

On 2017-04-21 16:23, Philipp Zabel wrote:
> On Thu, 2017-04-13 at 18:43 +0200, Peter Rosin wrote:
> [...]
>> +int mux_chip_register(struct mux_chip *mux_chip)
>> +{
>> +	int i;
>> +	int ret;
>> +
>> +	for (i = 0; i < mux_chip->controllers; ++i) {
>> +		struct mux_control *mux = &mux_chip->mux[i];
>> +
>> +		if (mux->idle_state == mux->cached_state)
>> +			continue;
> 
> I think this should be changed to
>  
> -               if (mux->idle_state == mux->cached_state)
> +               if (mux->idle_state == mux->cached_state ||
> +                   mux->idle_state == MUX_IDLE_AS_IS)
>                         continue;
> 
> or the following mux_control_set will be called with state ==
> MUX_IDLE_AS_IS. Alternatively, mux_control_set should return when passed
> this value.

That cannot happen because ->cached_state is initialized to -1
in mux_chip_alloc, so should always be == MUX_IDLE_AS_IS when
registering. And drivers are not supposed to touch ->cached_state.
I.e., ->cached_state is "owned" by the core.

Cheers,
peda

>> +		ret = mux_control_set(mux, mux->idle_state);
>> +		if (ret < 0) {
>> +			dev_err(&mux_chip->dev, "unable to set idle state\n");
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	ret = device_add(&mux_chip->dev);
>> +	if (ret < 0)
>> +		dev_err(&mux_chip->dev,
>> +			"device_add failed in mux_chip_register: %d\n", ret);
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(mux_chip_register);
> 
> regards
> Philipp
>