Re: [PATCH V2 3/3] cfg80211: support ieee80211-freq-limit DT property

On 2 January 2017 at 15:04, Johannes Berg [off-list ref] wrote:

Perhaps a better approach would be to not combine this with wiphy
registration, but require drivers that may use this to call a new
helper function *before* wiphy registration (and *after* calling
set_wiphy_dev()), like e.g.

   ieee80211_read_of_data(wiphy);

(...)

Yes, this would mean that it doesn't automatically get applied to
arbitrary drivers, but it seems unlikely that arbitrary drivers like
realtek USB would suddenly get OF node entries ... so that's not
necessarily a bad thing.

In the documentation for this function you could then document that it
will modify flags, and as such must not be called when the sband and
channel data is shared, getting rid of the waste/complexity of the copy
you otherwise have to make in cfg80211.

I just think it may be better to stick to something like
ieee80211_read_of_freq_limits
or
wiphy_read_of_freq_limits

As you noted this function will be a bit specific because of modifying
(possibly shared) band channels. At some point we may want to add more
helpers for other OF properties which won't have extra requirements
for driver code. Some drivers may want to use them while not necessary
risking have shared band channels modified.

-- 
Rafał
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