linux-kernel - Re: [PATCH V4 3/3] pwm: pxa: add device tree support

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Date:	Mon, 13 May 2013 13:04:36 +0800
From:	Chao Xie <xiechao.mail@...il.com>
To:	Eric Miao <eric.y.miao@...il.com>
Cc:	Chao Xie <chao.xie@...vell.com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 3/3] pwm: pxa: add device tree support

>> +       const struct of_device_id *of_id =
>> +                       of_match_device(pxa_pwm_of_match, &pdev->dev);
>> +       unsigned int npwm;
>> +
>> +       if (!of_id)
>> +               return -ENODEV;
>> +
>> +       npwm = (unsigned int)of_id->data;
>> +       pwm->chip.npwm = (npwm & HAS_SECONDARY_PWM) ? 2 : 1;
>> +
>> +       return 0;
>> +}
>> +
>>  static int pwm_probe(struct platform_device *pdev)
>>  {
>>         const struct platform_device_id *id = platform_get_device_id(pdev);
>> @@ -144,7 +180,6 @@ static int pwm_probe(struct platform_device *pdev)
>>         pwm->chip.dev = &pdev->dev;
>>         pwm->chip.ops = &pxa_pwm_ops;
>>         pwm->chip.base = -1;
>> -       pwm->chip.npwm = (id->driver_data & HAS_SECONDARY_PWM) ? 2 : 1;
>>
>>         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>         if (r == NULL) {
>> @@ -156,6 +191,20 @@ static int pwm_probe(struct platform_device *pdev)
>>         if (IS_ERR(pwm->mmio_base))
>>                 return PTR_ERR(pwm->mmio_base);
>>
>> +       if (!id) {
>> +               if (IS_ENABLED(CONFIG_OF))
>> +                       ret = pxa_pwm_parse_data_dt(pdev, pwm);
>> +               else
>> +                       ret = -ENODEV;
>> +       } else {
>> +               pwm->chip.npwm = (id->driver_data & HAS_SECONDARY_PWM) ? 2 : 1;
>> +       }
>
> ^^ braces not necessarily here, and I'm not really sure if we should check
> CONFIG_OF firstly, and leave the platform_device_id thing as a legacy
> fall back, what do you think?
>
>   if (IS_ENABLED(CONFIG_OF)) {
>      ...
>   } else {
>     const struct platform_device_id *id = platform_get_device_id(...);
>     ...
>   }
>
it has some reasons.
You ways works for
     1. PWM defined in DT configuration file and CONFIG_OF is defined
     2. CONFIG_OF is not defined.
If COFNIG_OF is defined, but PWM is not defined in device tree
configuration file. The device
can still match the driver is the id_table is matched or name is matched.
So I covered addtional situation
    1. PWM is not defined in DT configuration file but CONFIG_OF is defined.

So i keep the possiblility that event CONFIG_OF is defined, but PWM is
not defined in DT file, and we still can use old way to probe the
device.

>> +
>> +       if (ret) {
>> +               dev_err(&pdev->dev, "failed to parse data from device id\n");
>> +               return ret;
>> +       }
>> +
>>         ret = pwmchip_add(&pwm->chip);
>>         if (ret < 0) {
>>                 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
>> @@ -181,6 +230,7 @@ static struct platform_driver pwm_driver = {
>>         .driver         = {
>>                 .name   = "pxa25x-pwm",
>>                 .owner  = THIS_MODULE,
>> +               .of_match_table = pxa_pwm_of_match,
>>         },
>>         .probe          = pwm_probe,
>>         .remove         = pwm_remove,
>> --
>> 1.7.4.1
>>
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