Re: [PATCH 08/10] mac80211: Support on-channel scan option.

[Ben Greear <greearb@xxxxxxxxxxxxxxx>]

On 04/11/2012 08:45 PM, Johannes Berg wrote:
> On Wed, 2012-04-11 at 10:52 -0700, greearb@xxxxxxxxxxxxxxx wrote:
>
> >   static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
> >   				  struct cfg80211_scan_request *req)
> > @@ -438,10 +461,43 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
> >   	local->scan_req = req;
> >   	local->scan_sdata = sdata;
> >
> > -	if (local->ops->hw_scan)
> > +	if (local->ops->hw_scan) {
> >   		__set_bit(SCAN_HW_SCANNING,&local->scanning);
> > -	else
> > -		__set_bit(SCAN_SW_SCANNING,&local->scanning);
> > +	} else {
> > +		/* If we are scanning only on the current channel, then
> > +		 * we do not need to stop normal activities
> > +		 */
> > +		if ((req->n_channels == 1)&&
> > +		    (req->channels[0]->center_freq ==
> > +		     local->hw.conf.channel->center_freq)) {
>
> how about "else if {", then the indentation isn't so deep and you can
> have much nicer code in the entire block :)
>
> > +			unsigned long next_delay;
>
> please add a blank line after variable declarations.
>
> > +		}
> > +		else {
>
> please read the coding style documentation
>
> > @@ -672,6 +704,12 @@ void ieee80211_scan_work(struct work_struct *work)
> >
> >   	sdata = local->scan_sdata;
> >
> > +	/* When scanning on-channel, the first-callback means completeed. */
>
> typo "completed"

Ok, will fix all of that.


> > +	if (test_bit(SCAN_ONCHANNEL_SCANNING,&local->scanning)) {
> > +		aborted = test_and_clear_bit(SCAN_ABORTED,&local->scanning);
> > +		goto out_complete;
> > +	}
>
> how does the onchannel bit get cleared?

__ieee80211_scan_completed sets local->scanning to 0, and it
will WARN_ON if local->scanning is NOT zero when entering
the method, so I don't think I should clear it earlier.

> Shouldn't you be calling pre/post scan hooks?

Probably so...I'll add that.  Doesn't look like ath9k uses
it, but maybe some other NIC does need it.

> I'm a bit divided over this. On the one hand, it seems like a mildly
> useful optimisation, on the other though it adds a bunch of complexity
> for multi-channel we've been thinking about... Not that we want to
> support multi-channel with SW scan anyway, but still.

It's just an optimization...maybe just add a check and do a regular scan
if multi-channel is active if it's difficult to just make it work with
multi-channel?

Thanks,
Ben

> johannes


--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com

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