| Message ID | 1450364392-76874-1-git-send-email-zhaoxiu.zeng@gmail.com |
|---|---|
| State | Awaiting Upstream, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, 2015-12-17 at 22:59 +0800, Zeng Zhaoxiu wrote: > If the result of adding the first set bit to the mask is power of 2, > the mask must be contiguous. "mask & -mask" can get the first set bit > of mask gracefully. > - if (__ffs64(mask) + hweight64(mask) != fls64(mask)) > { > + inc = (mask & -mask); > + val = mask + inc; > + if ((val & (val - 1)) != 0) { > /* not a contiguous mask ... not handled now! */ Hm. Ok, I can see how that would work, but it doesn't really seem like much of an "improvement" to me? Surely I seem to need much more thinking to understand this. There's no reason to optimise it either, so why should we change it? johannes -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c index c9e325d..4c896e8 100644 --- a/net/mac80211/iface.c +++ b/net/mac80211/iface.c @@ -1628,7 +1628,9 @@ static void ieee80211_assign_perm_addr(struct ieee80211_local *local, ((u64)m[2] << 3*8) | ((u64)m[3] << 2*8) | ((u64)m[4] << 1*8) | ((u64)m[5] << 0*8); - if (__ffs64(mask) + hweight64(mask) != fls64(mask)) { + inc = (mask & -mask); + val = mask + inc; + if ((val & (val - 1)) != 0) { /* not a contiguous mask ... not handled now! */ pr_info("not contiguous\n"); break; @@ -1649,7 +1651,6 @@ static void ieee80211_assign_perm_addr(struct ieee80211_local *local, ((u64)m[2] << 3*8) | ((u64)m[3] << 2*8) | ((u64)m[4] << 1*8) | ((u64)m[5] << 0*8); - inc = 1ULL<<__ffs64(mask); val = (start & mask); addr = (start & ~mask) | (val & mask); do {
If the result of adding the first set bit to the mask is power of 2, the mask must be contiguous. "mask & -mask" can get the first set bit of mask gracefully. Signed-off-by: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.com> --- net/mac80211/iface.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)