Message-ID: <1ba2fa240809270408i1eab50f7lb48739d75deab676@mail.gmail.com> (sfid-20080927_130901_045261_5C5D9770)
Date: Sat, 27 Sep 2008 14:08:54 +0300
From: "Tomas Winkler" <tomasw@gmail.com>
To: "Ivo van Doorn" <ivdoorn@gmail.com>
Subject: Re: [PATCH RFC] mac80211: notify mac80211 about rfkill events
Cc: "Johannes Berg" <johannes@sipsolutions.net>,
	linville@tuxdriver.com, yi.zhu@intel.com, hmh@hmh.eng.br,
	linux-wireless@vger.kernel.org,
	"Emmanuel Grumbach" <emmanuel.grumbach@intel.com>
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References: <1222357719-26294-1-git-send-email-tomas.winkler@intel.com>
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On Sat, Sep 27, 2008 at 11:12 AM, Ivo van Doorn <ivdoorn@gmail.com> wrote:
> On Saturday 27 September 2008, Tomas Winkler wrote:
>> >> > That's definitely other option we wanted to suggest that mac80211
>> >> > would register itself to rfkill subsystem and will provide to driver
>> >> > appropriate callbacks.  The question is how  drivers vary in the rfkil
>> >> > implementation and whether it wouldn't be more complex, in that case
>> >> > the notification is quite clean solution.
>> >>
>> >> How complex does it have to be?
>>
>> > Not really, probably it only needs to be a wrapper around rfkill_force_state
>> > where we can use the RFKILL_ defines to indicate the BLOCKED status.
>>
>> Implementation wise it's more complicated since you have to teach each
>> driver under mac80211, this mean more
>> code and more bugs but I'm not sure this is the objective on this list
>> :) As opposite to just notifying mac about a rfkill
>> event so it's not trying to configure to access device, etc.
>
> Those driver that do generate RFKILL events already have the rfkill structure
> implemented, so for those drivers they only have to remvoe that code and just
> call the mac80211 rfkill handler when the RFKILL key is pressed.
> All other drivers which don't have a rfkill button don't have to do anything because
> mac80211 handles everything for them.

Each driver has to implement the low level of rfkill. I'm not sure how
mac80211 could handle it.

>
>> >> > > That means that the only change needed in ieee80211_ioctl_siwtxpower() is
>> >> > > only allowing the enabling of the radio when RFKILL is not set to BLOCKED.
>> >> >
>> >> > That's just complicates everything and moving the policy  decisions to
>> >> > the driver after all even
>> >> > form txpower off you implement it as soft rfkill.
>> >
>> > Why does it complicate things? It means that mac80211 doesn't use
>> > rfkill_force_state() when the user triggers a radio state change using
>> > iw/iwconfig/ifconfig or whatever userspace tool.
>>
>> I'm not sure I understand your intention, how do you plane to kill
>> radio then in this case, you are still to obliged to do so.
>
> Correct, and you can still do that using the approach how it is currently implemented
> in mac80211. Calling config() with the disable_radio field set.

This is wrong approach you are pushing more policy into driver.

>
> I am just saying that userspace commands like:
>        ifconfig wlan0 up
>        iwconfig wlan0 txpower on
> are not RFKILL events which are handled by the rfkill layer. Those are userspace commands
> which can simply be handled by mac80211. The rfkill layer is there to support events
> when a user presses the RFKILL button/key/slider on the device or laptop.

wlan0 up is not rfkill event but txpower on/off definitely provide
rfkill line as defiend in Henriques doc  and has affect on rfkill
state separating them just creates more confusion.
This is trying to create two APIs for the same thing both paths just
results into software rfkill  and this just pushes arbitration too low
into the driver. Driver should be just notified if to kill or arise
from death the radio

> See the discussion between Henrique and me
>        "[RFC] b43: A patch for control of the radio LED using rfkill"
> from last week.
>
>> > mac80211 doesn't generate rfkill events because it isn't tied to any device
>> > keys/buttons/sliders. That is what the drivers do. And they should only listen
>> > to that key/button/slider.
>>
>> writing 0 to sysfs file is not a button either it sill should soft
>> kill the radio.
>
> Well that feature was requested by others to create simple RFKILL event listeners
> in userspace to toggle the radio through the rfkill interface. Since using that interface
> you can simply toggle the radio state for all devices of the same type.
>

>> The sw switch is here to enable
>> killing and enabling radio from software. All the buttons stuff should
>> go under hard switches.
>
> Where is it documented that the RFKILL_STATE_SOFT_BLOCKED is for events from software?

It's definitely affected if I call radio.disabled through mac->config

> RFKILL_STATE_HARD_BLOCKED was called into life for non-overridable RFKILL states, not
> to allow for software states to be handled in rfkill.
>

> The rfkill layer is not the global radio state handler for any wireless device, it is the radio
> state handler for RFKILL events coming from actually pressing RFKILL keys on hardware.

I cannot say I like this definition, again it creates opening for too
many APIs doing the same thing.

>> > Come to think of it, there is a bug in the previous patch since it doesn't handle
>> > the case when the interface is brought up during a BLOCKED state.
>> >
>>
>> what is the p previous patch?  If you mean the one I've sent, then
>> it's known to be incomplete, it was produced to invoke this
>> conversation.
>
> I understand, I just wanted to make a note of it.
>
>> > So all that has to be done is:
>> >        * rfkill BLOCK event received in mac80211
>> >        * set flag to indicate the BLOCKED state
>> >        * disable radio
>>
>> In case of notification chain you don't disable radio from mac80211
>>
>> >        * prevent radio being enabled through ifup
>> >        * prevent radio being enabled through iwconfig txpower on
>> >
>> >        * rfkill UNBLOCK event received from mac80211
>> >        * clear flag to indicate UNBLOCKED state
>> >        * restore radio to the by iwconfig/ifup configured state
>> Same here.
>> Tomas
>
> All the more reason then to use the rfkill structure directly instead of
> using the notification system.

You contradict your self. If rfkill subsystem is to handle just button
events  why it doesn't just handle the rfill state notifications

Tomas