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

From: [email-masked] (Ezequiel Garcia)
Date: Sat, 31 Aug 2013 14:04:23 -0300

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?

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.
-- 
Ezequiel Garc?a, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com