Re: [PATCH] mtd: atmel_nand: fix the warning when CONFIG_OF is not defined

[Josh Wu <josh.wu@atmel.com>]

Hi, Ezequiel

On 9/1/2013 1:04 AM, Ezequiel Garcia wrote:
> On Fri, Aug 30, 2013 at 09:23:53PM +0100, David Woodhouse wrote:
>> On Wed, 2013-08-07 at 11:36 +0800, Josh Wu wrote:
>>> This patch fix following warning:
>>>
>>> drivers/mtd/nand/atmel_nand.c:2007: warning: 'atmel_nand_nfc_match' defined but not used
>>>
>>> This patch add '#if defined(CONFIG_OF)' block to guard around the definition of
>>> atmel_nand_nfc_match, in order to avoid the warning when kernel is configurated
>>> as non-dt supported.
>> Ick. This driver is littered with CONFIG_OF checks. Yet I've just seen a
>> patch to pxa3xx_nand which *removes* ifdefs, on the basis that all the
>> of_match_ functions/macros will just 'do the right thing'. Can't we do
>> that here too? We might just need to add __maybe_unused?
>>
> We can. We just need to provide a few dummy functions in linux/of_mtd.h
> just like the other of_xxx() are doing. See below!
>
>>> +#if defined(CONFIG_OF)
>>>   static struct of_device_id atmel_nand_nfc_match[] = {
>>>   	{ .compatible = "atmel,sama5d3-nfc" },
>>>   	{ /* sentinel */ }
>>>   };
>>> +#endif
>> Also, why doesn't this one appear in a MODULE_DEVICE_TABLE() ?
>>
> Indeed. And why doesn't it have a "const" keyword?

Thanks to point these out.

>
> So, in order to remove the CONFIG_OF safely from this driver,
> and avoid any stupid warnings, we need to first implement
> these dummies:
>
> --------------------------------8<-----------------------------------
> diff --git a/include/linux/of_mtd.h b/include/linux/of_mtd.h
> index ed7f267..66f173e 100644
> --- a/include/linux/of_mtd.h
> +++ b/include/linux/of_mtd.h
> @@ -14,6 +14,21 @@
>   int of_get_nand_ecc_mode(struct device_node *np);
>   int of_get_nand_bus_width(struct device_node *np);
>   bool of_get_nand_on_flash_bbt(struct device_node *np);
> +#else
> +static inline int of_get_nand_ecc_mode(struct device_node *np)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int of_get_nand_bus_width(struct device_node *np)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline bool of_get_nand_on_flash_bbt(struct device_node *np)
> +{
> +	return false;
> +}
>   #endif
>   
>   #endif /* __LINUX_OF_MTD_H */
> -------------------------------->8-----------------------------------
>
> And then, with this little patch, we get rid of the ugly CONFIG_OF check
> from the atmel_nand driver:
>
> --------------------------------8<-----------------------------------
> diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
> index 0e365da..ac58098 100644
> --- a/drivers/mtd/nand/atmel_nand.c
> +++ b/drivers/mtd/nand/atmel_nand.c
> @@ -1448,7 +1448,6 @@ static void atmel_nand_hwctl(struct mtd_info *mtd, int mode)
>   		ecc_writel(host->ecc, CR, ATMEL_ECC_RST);
>   }
>   
> -#if defined(CONFIG_OF)
>   static int atmel_of_init_port(struct atmel_nand_host *host,
>   			      struct device_node *np)
>   {
> @@ -1456,7 +1455,7 @@ static int atmel_of_init_port(struct atmel_nand_host *host,
>   	u32 offset[2];
>   	int ecc_mode;
>   	struct atmel_nand_data *board = &host->board;
> -	enum of_gpio_flags flags;
> +	enum of_gpio_flags flags = 0;
>   
>   	if (of_property_read_u32(np, "atmel,nand-addr-offset", &val) == 0) {
>   		if (val >= 32) {
> @@ -1539,13 +1538,6 @@ static int atmel_of_init_port(struct atmel_nand_host *host,
>   
>   	return 0;
>   }
> -#else
> -static int atmel_of_init_port(struct atmel_nand_host *host,
> -			      struct device_node *np)
> -{
> -	return -EINVAL;
> -}
> -#endif
>   
>   static int __init atmel_hw_nand_init_params(struct platform_device *pdev,
>   					 struct atmel_nand_host *host)
> @@ -2205,14 +2197,12 @@ static int __exit atmel_nand_remove(struct platform_device *pdev)
>   	return 0;
>   }
>   
> -#if defined(CONFIG_OF)
>   static const struct of_device_id atmel_nand_dt_ids[] = {
>   	{ .compatible = "atmel,at91rm9200-nand" },
>   	{ /* sentinel */ }
>   };
>   
>   MODULE_DEVICE_TABLE(of, atmel_nand_dt_ids);
> -#endif
>   
>   static int atmel_nand_nfc_probe(struct platform_device *pdev)
>   {
> @@ -2251,12 +2241,11 @@ static int atmel_nand_nfc_probe(struct platform_device *pdev)
>   	return 0;
>   }
>   
> -#if defined(CONFIG_OF)
> -static struct of_device_id atmel_nand_nfc_match[] = {
> +static const struct of_device_id atmel_nand_nfc_match[] = {
>   	{ .compatible = "atmel,sama5d3-nfc" },
>   	{ /* sentinel */ }
>   };
> -#endif
> +MODULE_DEVICE_TABLE(of, atmel_nand_nfc_match);
>   
>   static struct platform_driver atmel_nand_nfc_driver = {
>   	.driver = {
> -------------------------------->8-----------------------------------
>
> Of course, these are untested. If they look OK and don't cause any trouble,
> then I'll prepare proper patches.

Looks nice to me. Your proposal patch does the right thing to remove the 
CONFIG_OF.
So please sent them out. ;)

Best Regards,
Josh Wu