Re: [PATCH 1/2] mtd: atmel_nand: remove unneeded ifdef CONFIG_OF

+ devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

On Fri, Sep 13, 2013 at 05:28:13PM +0800, Josh Wu wrote:

On 9/12/2013 7:02 AM, Brian Norris wrote:

quoted

On Tue, Sep 03, 2013 at 05:20:27PM +0800, Josh Wu wrote:

quoted

Since following commit
  f3b391425d21e6138e57b2432d91134e0bc2b975

...

quoted

quoted

  (of_mtd: Add no-op stubs to support CONFIG_OF=n)

implements the stub for CONFIG_OF=n. Now we can safely remove all
CONFIG_OF in atmel_nand. (Thanks to Ezequiel Garcia's for this protype)

I'm not quite so sure about this patch, as I was about the pxa3xx patch.
With pxa3xx, the compiler can easily tell that pxa3xx_nand_probe_dt()
will return 0 without doing anything in the !CONFIG_OF case (and so will
likely remove the dead code), so it's no benefit to have the #ifdef. But
in this driver, the atmel_of_init_port() function can't be trivially
determined to do nothing (and in fact, it does something in either
CONFIG_OF=y or =n case). It's only protected by the 'if
(pdev->dev.of_node)' check, which the compiler can't predict.

I understand your concern here.

quoted

So, I don't know if we should remove the #ifdef at the expense of likely
significantly larger code. I won't protest, but I won't merge it yet
either. Perhaps others have better ideas, or perhaps you can find a good
way to work around this -- e.g., check the of_* helpers for -ENOSYS early
in atmel_of_init_port()?

So what about to add one more check： "IS_ENABLE(CONFIG_OF)" in
atmel_nand_probe().
And which is compiler predictable.

if (IS_ENABLED(CONFIG_OF) && pdev->dev.of_node) {
/* of_node can be parsed only when CONFIG_OF is enable */
res = atmel_of_init_port(host, pdev->dev.of_node);
if (res)
goto err_nand_ioremap;
} else {
... ...
}

That looks good to me. And it has precedent, a nearly identical patch
here:

  commit e305062e94719ef543ae936dd56501b5a36406c6
  Author: Laurent Pinchart [off-list ref]
  Date:   Tue Jun 18 12:29:49 2013 +0200

      gpio-rcar: Remove #ifdef CONFIG_OF around OF-specific sections

      All functions and data types used by OF-specific code paths are declared
      in <linux/of.h> regardless of CONFIG_OF. Replace the #ifdef CONFIG_OF
      guard with a if(IS_ENABLED(CONFIG_OF)) and let the compiler optimize
      the unused code away.

      Signed-off-by: Laurent Pinchart [off-list ref]
      Signed-off-by: Simon Horman [off-list ref]

Brian

(leaving context intact)

quoted

quoted

Signed-off-by: Josh Wu <redacted>
---
 drivers/mtd/nand/atmel_nand.c |   14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
index 060feea..1ca0724 100644
--- a/drivers/mtd/nand/atmel_nand.c
+++ b/drivers/mtd/nand/atmel_nand.c

@@ -1449,7 +1449,6 @@ 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)
 {

@@ -1457,7 +1456,7 @@ 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) {

@@ -1540,13 +1539,6 @@ 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)

@@ -2207,14 +2199,12 @@ 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)
 {

@@ -2253,12 +2243,10 @@ 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[] = {
 	{ .compatible = "atmel,sama5d3-nfc" },
 	{ /* sentinel */ }
 };
-#endif
 static struct platform_driver atmel_nand_nfc_driver = {
 	.driver = {

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