Subject: Re: [PATCH v3 1/3] usb: fsl-mxc-udc: replace cpu_is_xxx() with platform_device_id

From: Marc Kleine-Budde <[email-masked]>
Date: Mon, 14 Jan 2013 11:50:41 +0100

On 01/14/2013 11:39 AM, Felipe Balbi wrote:
> On Mon, Jan 14, 2013 at 11:34:05AM +0100, Marc Kleine-Budde wrote:
>> On 01/14/2013 11:24 AM, Felipe Balbi wrote:
>>> On Mon, Jan 14, 2013 at 11:18:53AM +0100, Marc Kleine-Budde wrote:
>>>> On 01/14/2013 11:16 AM, Felipe Balbi wrote:
>>>>> Hi,
>>>>>
>>>>> On Mon, Jan 14, 2013 at 06:12:39PM +0800, Peter Chen wrote:
>>>>>> @@ -2756,22 +2753,41 @@ static int fsl_udc_otg_resume(struct device *dev)
>>>>>>  
>>>>>>  	return fsl_udc_resume(NULL);
>>>>>>  }
>>>>>> -
>>>>>>  /*-------------------------------------------------------------------------
>>>>>>  	Register entry point for the peripheral controller driver
>>>>>>  --------------------------------------------------------------------------*/
>>>>>> -
>>>>>> +static const struct platform_device_id fsl_udc_devtype[] = {
>>>>>> +	{
>>>>>> +		.name = "imx-udc-mx25",
>>>>>> +		.driver_data = IMX25_UDC,
>>>>>> +	}, {
>>>>>> +		.name = "imx-udc-mx27",
>>>>>> +		.driver_data = IMX27_UDC,
>>>>>> +	}, {
>>>>>> +		.name = "imx-udc-mx31",
>>>>>> +		.driver_data = IMX31_UDC,
>>>>>> +	}, {
>>>>>> +		.name = "imx-udc-mx35",
>>>>>> +		.driver_data = IMX35_UDC,
>>>>>> +	}, {
>>>>>> +		.name = "imx-udc-mx51",
>>>>>> +		.driver_data = IMX51_UDC,
>>>>>> +	}
>>>>>> +};
>>>>>
>>>>> I wonder if your driver-data is actually needed since you can use string
>>>>> comparisson to achieve the exact same outcome.
>>>>
>>>> Why use a string compare, if the kernel infrastructure already does this
>>>> for you?
>>>
>>> what do you mean ? What kernel infrastructure is doing waht for me ?
>>
>> The kernel infrastructure is doing the string compare for you to match
>> the device against the driver (via platform_device_id->name). You get
>> the a pointer to the driver_data for free. So you don't need any string
>> compare in the driver later.
> 
> but current driver data is just duplicating name with an integer, it's
> pretty useless driver data.

I don't think so - another argument:
Less code. As struct platform_device_id is a static array the space is
allocated anyway. So it doesn't make any difference if driver_data is
NULL or not. Later you just need to make an integer comparison instead
of a call to a strcmp(), if you have a switch/case and IMX*_UDC is an
enum, the compiler will warn you if you've missed an IMX variant.

Marc

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