Re: [RFC v3 12/13] cfg80211: add channel checking for iface combinations

[Michal Kazior <michal.kazior@tieto.com>]

Johannes Berg wrote:
> On Tue, 2012-06-26 at 14:30 +0200, Michal Kazior wrote:
>
>> +#define CFG80211_MAX_NUM_DIFFERENT_CHANNELS 10
>
> Might make sense to put this into cfg80211.h, since e.g. hwsim could
> support this many channels?
>
>> +		cfg80211_get_chan_state(rdev, wdev_iter, &ch, &chmode);
>> +
>> +		switch (chmode) {
>> +		case CHAN_MODE_UNDEFINED:
>> +			break;
>> +		case CHAN_MODE_SHARED:
>> +			for (i = 0; i < CFG80211_MAX_NUM_DIFFERENT_CHANNELS; i++)
>> +				if (!used_channels[i] || used_channels[i] == ch)
>> +					break;
>> +
>> +			BUG_ON(i == CFG80211_MAX_NUM_DIFFERENT_CHANNELS);
>
> I'd prefer not to use BUG_ON(), maybe WARN_ON() and return some error?
> It seems it could actually happen with buggy drivers that suddenly go
> above their num_different_channels by switching around themselves or
> something?

Hmm.. Now that I think of it we could probably hit the BUG_ON normally. 
Suppose a driver supports num_different_channels == 
CFG80211_MAX_NUM_DIFFERENT_CHANNELS. If cfg80211_can_use_iftype_chan is 
called with another different channel we will hit the BUG_ON, no?

I think we should either do a WARN_ON_ONCE here, or nothing actually. 
And return -EBUSY of course.


-- 
Pozdrawiam / Best regards, Michal Kazior.