Re: [PATCH 1/4] fix not-and/or errors

Roel Kluin
2007-10-18T14:38:52Z

Al Viro wrote:
> On Wed, Oct 17, 2007 at 03:46:43PM +0200, Roel Kluin wrote:
>> +++ b/drivers/misc/asus-laptop.c
>> @@ -322,7 +322,7 @@ static void write_status(acpi_handle handle, int out, int mask)
>>
>> switch (mask) {
>> case MLED_ON:
>> - out = !out & 0x1;
>> + out = !(out & 0x1);
>
> Not sure if that's what had been intended.

It seems to me if I look at the code, that it's intended to make a bool out of 'out'. That's
nonsense because of the precedence the ! will turn it into a boolean before the & 0x1.

x = !x & y behaves like x = !x for y != 0.
for y = 1 the behavior is even the same for x = !(x & y)
so it does not matter in this case, except for clarity. I'll make it out = !out.

>
>> @@ -2882,7 +2882,7 @@ static int st_int_ioctl(struct scsi_tape *STp, unsigned int cmd_in, unsigned lon
>> !(STp->use_pf & PF_TESTED)) {
>> /* Try the other possible state of Page Format if not
>> already tried */
>> - STp->use_pf = !STp->use_pf | PF_TESTED;
>> + STp->use_pf = !(STp->use_pf | PF_TESTED);
>
> Wrong. This code, ugly as it is, happens to be correct. Replacement
> isn't. I would rewrite it as ^= PF_TESTED | USE_PF; /* remove USE_PF, set *
> * PF_TESTED */
>
> The rest is covered by Alexey's patch and one I'd posted as followup.

ok, thanks, I'll correct and omit these in my follow up patch.

Roel