On Sat, Mar 3, 2012 at 12:09 AM, <vivekanandah@xxxxxxxxxxx> wrote: > hi, hi vivekanandah, > > i am new to the linux system and i am hoping that this is the right list to > mail for my query. > > I am presently working on linux kernel 3.1.4 and i was looking into the > mac80211 code and the scan implementation on the same. the present wireless-testing scan state machine is simplified by the johannes's patch http://comments.gmane.org/gmane.linux.kernel.wireless.general/80287 and easy to understand > > when the scan process is started, the station is supposed to send a null > frame with PM bit set, so that AP can buffer frames to the station. > > However, it is seen in code that when scan is initiated (software scan), > the ieee80211_offchannel_enable_all_ps(local, false); function is called, > since the flag is set to false, the NULL frame will not be sent out. also, > when the scan state changes to leaving operating channel, the vifs interface > is blocked. even here, i see that the flag setting is false for offchannel > Power save and the null frame is not sent out. the current wireless-testing tree does this. please look at ieee80211_start_sw_scan git clone git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-testing.git > > the comment however just prior to the vifs stop function call indicates that > offchannel settings are already completed at the start of scan process. the > code snippet is shown below: > > /*PS will already be in off-channel mode, we do that once at the beginning > of scanning.*/ > ieee80211_offchannel_stop_vifs(local, false); > > i just would like to know why the flag is FALSE in both cases, so we never > send out a null frame to the AP at the start. is this a bug or there is some > deficiency in my current understanding? based on my limited understanding of the previous code, my guess we have in ieee80211_work in work.c and this should send a null func frame. (both started and tmp_channel will be false and NULL if (on_oper_chan != on_oper_chan2) { if (on_oper_chan2) { /* going off oper channel, PS too */ ----> ieee80211_offchannel_stop_vifs(local, true); ieee80211_hw_config(local, 0); } else { /* going on channel, but leave PS its best to look at the current wireless-testing tree code, its more simpler. > > -- > 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 -- thanks, shafi -- 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
