Re: [PATCH] ath9k: Add module parameter to disable hardware crypto

[Jouni Malinen <j@w1.fi>]

On Tue, Feb 24, 2009 at 05:15:49PM +0100, Michael Buesch wrote:
> On Tuesday 24 February 2009 12:42:01 Jouni Malinen wrote:
> >  #define CHAN2G(_freq, _idx)  { \
> > @@ -1587,7 +1591,7 @@ int ath_attach(u16 devid, struct ath_sof
> >  		IEEE80211_HW_SUPPORTS_PS |
> >  		IEEE80211_HW_PS_NULLFUNC_STACK;
> >  
> > -	if (AR_SREV_9160_10_OR_LATER(sc->sc_ah))
> > +	if (AR_SREV_9160_10_OR_LATER(sc->sc_ah) || modparam_nohwcrypt)
> >  		hw->flags |= IEEE80211_HW_MFP_CAPABLE;
> 
> Are you sure this is correct?

I have no reason to believe otherwise.

> The hardware capability doesn't magically change by switching a modparam.

Of course not.

> Either the HW is MFP capable or it isn't.

It is not that simple. Hardware is MFP capable with software
encryption/decryption in all cases; it just may not work correctly if
hardware acceleration is used with older hardware revisions.

> If hwcrypto is disabled (set_key returns error), mac80211 should be smart
> enough to do crypto (including MFP) in software anyway.

Yes and that is exactly what the patch is doing.. If nohwcrypt=1,
mac80211 takes care of crypto and MFP can be used. If nohwcrypt=0, MFP
is disabled for older hardware revisions (but enabled for new ones that
handle MFP without issues in hw crypto).

-- 
Jouni Malinen                                            PGP id EFC895FA