linux-kernel - Re: [PATCH v2 1/2] hwmon: (ucd9000) Add gpio chip interface

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Date:   Wed, 14 Mar 2018 14:01:34 -0500
From:   Eddie James <eajames@...ux.vnet.ibm.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     linux-hwmon@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Joel Stanley <joel@....id.au>,
        Christopher Bostic <cbostic@...ux.vnet.ibm.com>,
        Andrew Jeffery <andrew@...id.au>
Subject: Re: [PATCH v2 1/2] hwmon: (ucd9000) Add gpio chip interface



On 03/14/2018 01:55 PM, Guenter Roeck wrote:
> On Tue, Mar 13, 2018 at 11:13:04PM +0200, Andy Shevchenko wrote:
>> On Tue, Mar 13, 2018 at 10:59 PM, Eddie James
>> <eajames@...ux.vnet.ibm.com> wrote:
>>> From: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>>>
>>> Add a struct gpio_chip and define some methods so that this device's
>>> I/O can be accessed via /sys/class/gpio.
>>> +       /*
>>> +        * Note:
>>> +        *
>>> +        * Pinmux support has not been added to the new gpio_chip.
>>> +        * This support should be added when possible given the mux
>>> +        * behavior of these IO devices.
>>> +        */
>>> +       data->gpio.label = (const char *)&client->name;
>> Hmm... Why do you need this casting?
>>
>>> +       data->gpio.get_direction = ucd9000_gpio_get_direction;
>>> +       data->gpio.direction_input = ucd9000_gpio_direction_input;
>>> +       data->gpio.direction_output = ucd9000_gpio_direction_output;
>>> +       data->gpio.get = ucd9000_gpio_get;
>>> +       data->gpio.set = ucd9000_gpio_set;
>>> +       data->gpio.can_sleep = 1;
>> Isn't it type of boolean?
>>
> You are right.
>
>>> +       data->gpio.base = -1;
>>> +       data->gpio.parent = &client->dev;
>>> +       data->gpio.owner = THIS_MODULE;
>>> +       data->gpio.of_node = client->dev.of_node;
>> I think GPIO core does this for you.
>>
> Same here. I checked and found that it also sets the owner, so maybe this can be
> dropped as well.

Ah true. Especially since there is a TODO: remove chip->owner in the core.

>
>>> +       if (data->gpio.ngpio) {
>> Hmm...
>>
>> I would rather reorganize the above part to a separate helper, like
>>
>> static int ..._probe_gpio()
>> {
>> ...
>>    switch () {
>>     default:
>>       return 0; /* GPIO part is optional */
>>    }
>>    return 0;
>> }
>>
>> ret = _probe_gpio();
>> if (ret)
>>   dev_warn();
>>
> I am neutral to positiva on that.
> Might as well add the call to devm_gpiochip_add_data()
> into that function as well.

Sure. I can do a v4.

Thanks,
Eddie

>
>>> +               ret = devm_gpiochip_add_data(&client->dev, &data->gpio,
>>> +                                            client);
>>> +               if (ret)
>>> +                       dev_warn(&client->dev, "Could not add gpiochip: %d\n",
>>> +                                ret);
>>> +       }
>>> +
>>>          return pmbus_do_probe(client, mid, info);
>>>   }
>>>
>>> --
>>> 1.8.3.1
>>>
>>
>>
>> -- 
>> With Best Regards,
>> Andy Shevchenko