drivers/rtc/rtc-r9701.c: fix crash in r9701_remove()

If probing the RTC didn't succeed due to failed RTC register access, the
RTC device will be unregistered.  Then, when removing the module
r9701_remove() causes a kernel crash while trying to unregister a not
registered RTC device.  Fix this by doing RTC register access test before
RTC device registration.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/rtc/rtc-r9701.c b/drivers/rtc/rtc-r9701.c
index 9beba49c3c5b48c2abcca65c916eabc0d782a49a..2853c2a6f10f4a055d2aadb8d3fac0380bff7f97 100644 (file)
--- a/drivers/rtc/rtc-r9701.c
+++ b/drivers/rtc/rtc-r9701.c
@@ -125,6 +125,13 @@ static int __devinit r9701_probe(struct spi_device *spi)
        unsigned char tmp;
        int res;
 
+       tmp = R100CNT;
+       res = read_regs(&spi->dev, &tmp, 1);
+       if (res || tmp != 0x20) {
+               dev_err(&spi->dev, "cannot read RTC register\n");
+               return -ENODEV;
+       }
+
        rtc = rtc_device_register("r9701",
                                &spi->dev, &r9701_rtc_ops, THIS_MODULE);
        if (IS_ERR(rtc))
@@ -132,13 +139,6 @@ static int __devinit r9701_probe(struct spi_device *spi)
 
        dev_set_drvdata(&spi->dev, rtc);
 
-       tmp = R100CNT;
-       res = read_regs(&spi->dev, &tmp, 1);
-       if (res || tmp != 0x20) {
-               rtc_device_unregister(rtc);
-               return res;
-       }
-
        return 0;
 }