On Tue, 2015-11-10 at 09:52 +0100, Johannes Berg wrote: > From: Johannes Berg <johannes.berg@xxxxxxxxx> > > There are many drivers with different behaviour, but in a lot of > systems only a single driver will ever be built. In that case we > could practically get rid of the code for the paths that this > driver/device doesn't need. Doing that, however, would be rather > dangerous. > > As a decent alternative, use static keys to simply get into the > required code path for the single built driver. > > To achieve this associate with each flag an _ON and _OFF Kconfig > symbol. Selecting this symbol in a driver will cause the system > to take this as the default state (if both are selected, there's > no optimisation at all.) > > If, for example, the Kconfig selection said that a given flag is > expected to always be turned off, then the code depending on it > would be placed out-of-line and the jump to it NOPed out. If a > different driver that actually requires the code contrary to the > Kconfig selection is loaded, the jump will be patched in and the > first thing in the out-of-line section will be to check the real > hardware flag (since multiple drivers can be loaded.) > > Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> > --- [...] > diff --git a/net/mac80211/Kconfig.hwflags > b/net/mac80211/Kconfig.hwflags > new file mode 100644 > index 000000000000..06f6ba12c86e > --- /dev/null > +++ b/net/mac80211/Kconfig.hwflags > @@ -0,0 +1,192 @@ > +config MAC80211_HW_HAS_RATE_CONTROL_ON > + bool > + depends on MAC80211 > +config MAC80211_HW_HAS_RATE_CONTROL_OFF > + bool > + depends on MAC80211 > +config MAC80211_HW_RX_INCLUDES_FCS_ON > + bool > + depends on MAC80211 > +config MAC80211_HW_RX_INCLUDES_FCS_OFF > + bool > + depends on MAC80211 [...] Now that you have all these options in Kconfig, wouldn't it be possible to remove the calls to the "static" ieee80211_hw_set() in the drivers and somehow set all the flags that are defined in Kconfig automatically? The driver could still call ieee80211_hw_clear() and ieee80211_hw_set() if it needs to change dynamically. -- Luca. -- 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
