watchdog: s3c2410: Make s3c2410_get_wdt_drv_data() return an int

This is a preparation for making more use of dev_err_probe(). The idea
is that s3c2410_get_wdt_drv_data() (as it's called only by .probe()) can
make effective use of dev_err_probe() only if it returns an int. For
that the assignment to wdt->drv_data has to happen in the function. The
caller can then just pass on the return value in the error case.

This seems to be nicer for the compiler: bloatometer reports for an
ARCH=arm s3c6400_defconfig build:

	add/remove: 1/1 grow/shrink: 0/1 up/down: 4/-64 (-60)
	Function                                     old     new   delta
	__initcall__kmod_s3c2410_wdt__209_821_s3c2410wdt_driver_init6       -       4      +4
	__initcall__kmod_s3c2410_wdt__209_819_s3c2410wdt_driver_init6       4       -      -4
	s3c2410wdt_probe                            1332    1272     -60

There is no semantical change. (Just one minor difference: Before this
patch wdt->drv_data was always assigned, now that only happens in the
non-error case. That doesn't matter however as *wdt is freed in the
error case.)

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230307065603.2253054-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Author: Uwe Kleine-König

drivers/watchdog/s3c2410_wdt.c

@@ -579,8 +579,8 @@ static inline unsigned int s3c2410wdt_get_bootstatus(struct s3c2410_wdt *wdt)
 	return 0;
 }
 
-static inline const struct s3c2410_wdt_variant *
-s3c2410_get_wdt_drv_data(struct platform_device *pdev)
+static inline int
+s3c2410_get_wdt_drv_data(struct platform_device *pdev, struct s3c2410_wdt *wdt)
 {
 	const struct s3c2410_wdt_variant *variant;
 	struct device *dev = &pdev->dev;
@@ -603,24 +603,26 @@ s3c2410_get_wdt_drv_data(struct platform_device *pdev)
 					   "samsung,cluster-index", &index);
 		if (err) {
 			dev_err(dev, "failed to get cluster index\n");
-			return NULL;
+			return -EINVAL;
 		}
 
 		switch (index) {
 		case 0:
-			return variant;
+			break;
 		case 1:
-			return (variant == &drv_data_exynos850_cl0) ?
+			variant = (variant == &drv_data_exynos850_cl0) ?
 				&drv_data_exynos850_cl1 :
 				&drv_data_exynosautov9_cl1;
+			break;
 		default:
 			dev_err(dev, "wrong cluster index: %u\n", index);
-			return NULL;
+			return -EINVAL;
 		}
 	}
 #endif
 
-	return variant;
+	wdt->drv_data = variant;
+	return 0;
 }
 
 static void s3c2410wdt_wdt_disable_action(void *data)
@@ -644,9 +646,9 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
 	spin_lock_init(&wdt->lock);
 	wdt->wdt_device = s3c2410_wdd;
 
-	wdt->drv_data = s3c2410_get_wdt_drv_data(pdev);
-	if (!wdt->drv_data)
-		return -EINVAL;
+	ret = s3c2410_get_wdt_drv_data(pdev, wdt);
+	if (ret)
+		return ret;
 
 	if (wdt->drv_data->quirks & QUIRKS_HAVE_PMUREG) {
 		wdt->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,