linux-kernel - Re: [PATCH RFC] I2C: i2c-smbus: add device tree support

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Date:	Thu, 14 Apr 2016 11:37:25 +0200
From:	Andrea Merello <andrea.merello@...il.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	jdelvare@...e.de, Wolfram Sang <wsa@...-dreams.de>,
	linux-i2c@...r.kernel.org, devicetree <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] I2C: i2c-smbus: add device tree support

On Wed, Apr 13, 2016 at 7:58 PM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Wed, Apr 13, 2016 at 11:36 AM, Andrea Merello
> <andrea.merello@...il.com> wrote:
>> According to Documentation/i2c/smbus-protocol, a smbus controller driver
>> that wants to hook-in smbus extensions support, can call
>> i2c_setup_smbus_alert(). There are very few drivers that are currently
>> doing this.
>>
>> However the i2c-smbus module can also work with any
>> smbus-extensions-unaware I2C controller, as long as we provide an extra
>> IRQ line connected to the I2C bus ALARM signal.
>>
>> This patch makes it possible to go this way via DT. Note that the DT node
>> will indeed describe a (little) piece of HW, that is the routing of the
>> ALARM signal to an IRQ line (so it seems a fair DT use to me, but RFC).
>>
>> Note that AFAICT, by design, i2c-smbus module pretends to be an I2C slave
>> with address 0x0C (that is the alarm response address), and IMHO this is
>> quite consistent with usage in the DT as a I2C child node.
>
>> --- a/drivers/i2c/i2c-smbus.c
>> +++ b/drivers/i2c/i2c-smbus.c
>
>> @@ -137,20 +138,29 @@ static int smbalert_probe(struct i2c_client *ara,
>>         struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
>>         struct i2c_smbus_alert *alert;
>>         struct i2c_adapter *adapter = ara->adapter;
>> +       struct device_node *of_node = ara->dev.of_node;
>
> Perhaps fwnode_handle ?

Browsing the kernel tree it looks like using of_node is how almost all
drivers do. Any specific reason to go for fwnode_handle here?

Wouldn't this end up to just an extra is_of_node() and to_of_node() ?

>
>>         int res;
>> +       int irq_type;
>>
>>         alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
>>                              GFP_KERNEL);
>>         if (!alert)
>>                 return -ENOMEM;
>>
>> -       alert->alert_edge_triggered = setup->alert_edge_triggered;
>> -       alert->irq = setup->irq;
>> +       if (setup) {
>> +               alert->alert_edge_triggered = setup->alert_edge_triggered;
>> +               alert->irq = setup->irq;
>> +       } else if (of_node) {
>> +               alert->irq = irq_of_parse_and_map(of_node, 0);
>> +               irq_type = irq_get_trigger_type(alert->irq);
>> +               alert->alert_edge_triggered = (irq_type & IRQ_TYPE_EDGE_BOTH);
>> +       }
>
> --
> With Best Regards,
> Andy Shevchenko