On Mon, May 7, 2012 at 3:05 PM, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > On Mon, 2012-05-07 at 14:01 +0200, Janusz Dziedzic wrote: >> 2011/10/26 Arik Nemtsov <arik@xxxxxxxxxx>: >> > On Wed, Oct 26, 2011 at 11:59, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: >> >> On 10/23/2011 8:21 AM, Arik Nemtsov wrote: >> >>> >> >>> Some cards can generate CCMP IVs in HW, but require the space for the IV >> >>> to be pre-allocated in the frame at the correct offset. Add a key flag >> >>> that allows us to achieve this. >> >> >> >> Is it really that expensive to generate the IV and then not use it that this >> >> is worth the extra complexity? This not just makes it more complex but also >> >> more expensive in the other case. >> >> >> > >> > Some of the platforms with this chip are pretty weak (host CPU is the >> > bottleneck). >> > >> > We add another "if" for the other case (for a value that's likely in >> > the cacheline already). I don't think that's too bad. >> > >> >> Hello, >> Why this is only done for CCMP? >> Our firmware require such IVs allocation for all modes and currently >> we have common code that do that in the driver based on: >> iv_len = tx_info->control.hw_key->iv_len >> icv_len = tx_info->control.hw_key->icv_len >> >> /* cw1200 driver */ >> skb_push(t->skb, iv_len); >> memmove(newhdr, newhdr + iv_len, t->hdrlen); >> skb_put(t->skb, icv_len); >> .... >> >> Isn't better to handle all modes in mac80211 base on >> IEEE80211_KEY_FLAG_PUT_IV_SPACE or just leave this for the driver? >> >> I know this is easy to fix in our driver but still we have to remember >> that in case of CCMP mac80211 will already do it for us and will not >> do that in case of other modes. >> So, my proposal is to remove all changes from net/mac80211/wpa.c file >> and remember that driver should care about it - in such case >> PUT_IV_SPACE will be more generic. > > I suggest the opposite, make it more generic in mac80211. I agree with Johannes - it's better to do it in mac80211 and be aware of the extra tailroom requirement when allocating the skb. The wl12xx card only needs this for CCMP, you're welcome to extend this to other modes. But please make sure to allow selecting specific modes, not just all or nothing. Arik -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
