[PATCH 6/6] staging: dgap: tty.c: removes smatch warning "unsigned '--un->un_open_count' is never less than zero"

[Lidza Louina]

On Mon, Sep 23, 2013 at 8:00 PM, Dan Carpenter <dan.carpenter at oracle.com> wrote:
> On Mon, Sep 23, 2013 at 06:47:17PM -0400, Lidza Louina wrote:
>> This patch removes this smatch warning:
>> unsigned '--un->un_open_count' is never less than zero
>>
>> The code decremented the un_open_count variable
>> and tested to see if it was less than zero. Because
>> un_open_count is unsigned and can't be below zero,
>> this test doesn't work. This patch tests
>> un_open_count against 0 without decrementing it.
>>
>> Signed-off-by: Lidza Louina <lidza.louina at gmail.com>
>> ---
>>  drivers/staging/dgap/dgap_tty.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/dgap/dgap_tty.c b/drivers/staging/dgap/dgap_tty.c
>> index 8f0a824..f496710 100644
>> --- a/drivers/staging/dgap/dgap_tty.c
>> +++ b/drivers/staging/dgap/dgap_tty.c
>> @@ -1442,7 +1442,7 @@ static void dgap_tty_close(struct tty_struct *tty, struct file *file)
>>               un->un_open_count = 1;
>>       }
>>
>> -     if (--un->un_open_count < 0) {
>> +     if (un->un_open_count == 0) {
>>               APR(("bad serial port open count of %d\n", un->un_open_count));
>>               un->un_open_count = 0;
>>       }
>
> This fix isn't right.  We still need the decrement.  Probably the best
> thing is to audit all the driver and make sure that un->un_open_count
> can never be == 0.  But the next best, and still totally reasonable
> thing to do is this:
>
>         if (un->un_open_count == 0) {
>                 APR(("bad serial port open count of %d\n", un->un_open_count));
>                 un->un_open_count = 1;
>         }
>         un->un_open_count--;
>
> regards,
> dan carpenter
>

Okay, I see why, I'll resend this.