mtd: nand: make more readable panic_nand_wait_ready() and nand_wait_ready()

panic_nand_wait_ready() and nand_wait_ready() calls dev_ready() without checking if it exists. This patch add check routine dev_ready() before run dev_ready()
and this makes the code more readable

---
 drivers/mtd/nand/nand_base.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

index bd39f7b..110db78 100644
@@ -473,8 +473,10 @@ static void panic_nand_wait_ready(struct mtd_info *mtd, unsigned long timeo)
 
 	/* Wait for the device to get ready */
 	for (i = 0; i < timeo; i++) {
-		if (chip->dev_ready(mtd))
-			break;
+		if(chip->dev_ready){
+			if (chip->dev_ready(mtd))
+				break;
+		}
 		touch_softlockup_watchdog();
 		mdelay(1);
 	}

@@ -493,8 +495,10 @@ void nand_wait_ready(struct mtd_info *mtd)
 	led_trigger_event(nand_led_trigger, LED_FULL);
 	/* Wait until command is processed or timeout occurs */
 	do {
-		if (chip->dev_ready(mtd))
-			break;
+		if(chip->dev_ready){
+			if (chip->dev_ready(mtd))
+				break;
+		}
 		touch_softlockup_watchdog();
 	} while (time_before(jiffies, timeo));
 	led_trigger_event(nand_led_trigger, LED_OFF);

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There are many occasions where we call a function pointer without (locally) checking that it is non-NULL. That is by design.

If you see a problem with this behavior, please fix this properly rather than covering it up. This patch will just make faulty drivers spin for 20ms rather than hitting a bug. Instead, you should aim to fix buggy drivers that call dev_ready() without assigning it; or even better, defensively improve nand_base to detect those drivers which are utilizing nand_command_lp() or nand_command() without assigning dev_ready().

This patch does not make the code more readable, nor does it improve the state of the original code much. Please solve and document a real problem.

Thanks,
Brian