Re: [PATCH v2] net: bluetooth: hci_sock: Use 'const void *' instead of 'void *' for 2nd parameter of hci_test_bit()

Chen Gang S
2015-02-03T02:25:22Z

On 2/3/15 05:20, Joe Perches wrote:
> On Tue, 2015-02-03 at 05:14 +0800, Chen Gang S wrote:
>> hci_test_bit() does not modify 2nd parameter, so it is better to let it
>> be constant, or may cause build warning. The related warning (with
>> allmodconfig under xtensa):
> []
>> diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
> []
>> @@ -46,7 +46,7 @@ struct hci_pinfo {
>> unsigned short channel;
>> };
>>
>> -static inline int hci_test_bit(int nr, void *addr)
>> +static inline int hci_test_bit(int nr, const void *addr)
>> {
>> return *((__u32 *) addr + (nr >> 5)) & ((__u32) 1 << (nr & 31));
>> }
>
> It's probably better to use const __u32 * here too, but the
> real thing I wonder is whether or not there's an issue with
> one of the 2 uses of this function.
>
> One of them passes a unsigned long *, the other a u32 *.
>
> $ git grep -w hci_test_bit
> net/bluetooth/hci_sock.c:static inline int hci_test_bit(int nr, void *addr)
> net/bluetooth/hci_sock.c: if (!hci_test_bit(flt_event, &flt->event_mask))
> net/bluetooth/hci_sock.c: !hci_test_bit(ocf & HCI_FLT_OCF_BITS,
> net/bluetooth/hci_sock.c- &hci_sec_filter.ocf_mask[ogf])) &&
>
> hci_sec_filter.ocf_mask is __u32
> but flt->event_mask is unsigned long.
>
> Any possible issue here on 64-bit systems?
>

For me, it can not cause issue on 64-bit systems. hci_test_bit() treats
'addr' as "__u32 *", and has to use the pointer to do something.

Thanks.
--
Chen Gang

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