Re: [PATCH 2.6.27-rc3] led: driver for LEDs on PCEngines ALIX.2 and ALIX.3 boards

Stefan Richter
2008-08-24T10:09:22Z

Andrew Morton wrote:
> On Tue, 19 Aug 2008 22:23:41 +0500
> Constantin Baranov <const@const.mimas.ru> wrote:
>> --- linux-2.6.27-rc3/drivers/leds/leds-alix.c 1970-01-01 04:00:00.000000000 +0400
>> +++ linux-2.6.27-rc3-alix/drivers/leds/leds-alix.c 2008-08-19 21:59:05.207153570 +0500
...
>> +static int __init alix_led_probe(struct platform_device *pdev)
>> +{
>> + int i;
>> + int ret = 0;
>> +
>> + for (i = 0; i < ARRAY_SIZE(alix_leds) && ret >= 0; i++)
>> + ret = led_classdev_register(&pdev->dev, &alix_leds[i].cdev);
>> +
>> + if (ret < 0) {
>> + for (i = i - 2; i >= 0; i--)
>
> this is off-by-one, surely.
>
> If we get here with i==1, we'll loop 4 billion times.
>
>> + led_classdev_unregister(&alix_leds[i].cdev);
>> + }
>> +
>> + return ret;
>> +}
...
> How's this look?
...
> @@ -92,7 +95,7 @@ static int __init alix_led_probe(struct
> ret = led_classdev_register(&pdev->dev, &alix_leds[i].cdev);
>
> if (ret < 0) {
> - for (i = i - 2; i >= 0; i--)
> + while (--i >= 0)
> led_classdev_unregister(&alix_leds[i].cdev);
> }

Really? Constantin's code looks correct to me. He increments i once
more after failure.

Perhaps write it easier to read; i.e. in the same way as most error
return checks everywhere in the kernel:

for (i = 0; i < ARRAY_SIZE(alix_leds); i++) {
ret = led_classdev_register(...etc...);
if (ret < 0)
break;
}

if (ret < 0)
while (i--)
led_classdev_unregister(&alix_leds[i].cdev);

Or while (--i >= 0)

or for (i--; i >= 0; i--)
--
Stefan Richter
-=====-==--- =--- ==---