rtc: max8925: Initialize drvdata before registering device

Commit f44f7f96a20 ("RTC: Initialize kernel state from RTC") uncovered
an issue in a number of RTC drivers, where the drivers call
rtc_device_register before initializing the device or platform drvdata.

This frequently results in null pointer dereferences when the
rtc_device_register immediately makes use of the rtc device, calling
rtc_read_alarm.

The solution is to ensure the drvdata is initialized prior to registering
the rtc device.

CC: Wolfram Sang <w.sang@pengutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: rtc-linux@googlegroups.com
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/drivers/rtc/rtc-max8925.c b/drivers/rtc/rtc-max8925.c
index 20494b5..3bc046f 100644 (file)
--- a/drivers/rtc/rtc-max8925.c
+++ b/drivers/rtc/rtc-max8925.c
@@ -258,6 +258,8 @@ static int __devinit max8925_rtc_probe(struct platform_device *pdev)
        }
 
        dev_set_drvdata(&pdev->dev, info);
+       /* XXX - isn't this redundant? */
+       platform_set_drvdata(pdev, info);
 
        info->rtc_dev = rtc_device_register("max8925-rtc", &pdev->dev,
                                        &max8925_rtc_ops, THIS_MODULE);
@@ -267,10 +269,9 @@ static int __devinit max8925_rtc_probe(struct platform_device *pdev)
                goto out_rtc;
        }
 
-       platform_set_drvdata(pdev, info);
-
        return 0;
 out_rtc:
+       platform_set_drvdata(pdev, NULL);
        free_irq(chip->irq_base + MAX8925_IRQ_RTC_ALARM0, info);
 out_irq:
        kfree(info);