Subject: [PATCH] gpio: omap: make gpio numbering deterministical by using of aliases

From: [email-masked] (Grygorii Strashko)
Date: Tue, 14 Jun 2016 18:10:56 +0300

On 06/14/2016 03:01 PM, Uwe Kleine-K?nig wrote:
> Hello Grygorii,
> 
> On Tue, Jun 14, 2016 at 02:18:08PM +0300, Grygorii Strashko wrote:
>> On 06/14/2016 01:03 PM, Uwe Kleine-K?nig wrote:
>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>> index b98ede78c9d8..6814245a54aa 100644
>>> --- a/drivers/gpio/gpio-omap.c
>>> +++ b/drivers/gpio/gpio-omap.c
>>> @@ -1034,6 +1034,7 @@ static int omap_gpio_chip_init(struct gpio_bank *bank, struct irq_chip *irqc)
>>>    	static int gpio;
>>>    	int irq_base = 0;
>>>    	int ret;
>>> +	int gpio_alias_id;
>>>    
>>>    	/*
>>>    	 * REVISIT eventually switch from OMAP-specific gpio structs
>>> @@ -1056,6 +1057,17 @@ static int omap_gpio_chip_init(struct gpio_bank *bank, struct irq_chip *irqc)
>>>    		bank->chip.label = "gpio";
>>>    		bank->chip.base = gpio;
>>
>> I think, the gpio base correction should be done here
> 
> What is the upside of doing it here? It has the downside that it needs
> one more indention level. The only difference I see is that it doesn't
> apply for mpuio devices then and wonder if that is relevant.

Personally, I prefer not ti touch mpuio code unless really required.

>   
>>>    	}
>>> +
>>> +	/*
>>> +	 * Traditionally the base is given out in first-come-first-serve order.
>>> +	 * This might shuffle the numbering of gpios if the probe order changes.
>>> +	 * So make the base deterministical if the device tree specifies alias
>>> +	 * ids.
>>> +	 */
>>> +	gpio_alias_id = of_alias_get_id(bank->chip.of_node, "gpio");
>>> +	if (gpio_alias_id >= 0)
>>> +		bank->chip.base = bank->width * gpio_alias_id;
>>> +
>>
>> Unfortunately, this driver is still used by non-DT platforms, so above code will
>>   break build if !OF && !OF_GPIO
> 
> Without CONFIG_OF of_alias_get_id still exists and returns -ENOSYS which
> should make the added code a nop. Does your compiler agree with you that
> my patch breaks building the driver?

make ARCH=arm omap1_defconfig
make ARCH=arm ./drivers/gpio/gpio-omap.o

drivers/gpio/gpio-omap.c: In function 'omap_gpio_chip_init':
drivers/gpio/gpio-omap.c:1066:44: error: 'struct gpio_chip' has no member named 'of_node'
  gpio_alias_id = of_alias_get_id(bank->chip.of_node, "gpio");
                                            ^
make[1]: *** [drivers/gpio/gpio-omap.o] Error 1
make: *** [drivers/gpio/gpio-omap.o] Error 2

-- 
regards,
-grygorii