From: Chen Gang S [mailto:gang.chen@xxxxxxxxxxxxx] > On 2/5/15 05:09, Marcel Holtmann wrote: > > Hi Sergei, > > > >>>> -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)); > >>>> } > >> > >>> Is there a 'standard' function lurking that will do the above. > >>> On x86 the cpus 'bit test' instruction will handle bit numbers > >>> greater than the word size - so it can be a single instruction. > >> > >> Of course, there's test_bit(). > > > > we did leave hci_test_bit in the code since there are some userspace facing > > API that we can not change. Remember that the origin of this code is > > from 2.4.6 kernel. > > > > So we can only change this if you can ensure not to break the userspace API. > > So might want to write unit tests to ensure working HCI filter before even > > considering touching this. > > > > For me, we have to remain hci_test_bit(), it is for "__u32 *" (which we > can not change). The common test_bit() is for "unsigned long *", in this > case, I guess it may cause issue under 64-bit environments. Except that half the time you are passing a 'long *' and you haven't explained why this isn't broken on 64bit architectures. Note that on LE systems the size of the accesses used to access a dense bit array don't matter. This is not true of BE systems. David -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
