question about generalized way for RSSI notification

question about generalized way for RSSI notification

[Alexey Perevalov]

Dear wireless subsystem maintainers,

I have a question regarding RSSI notification to the user space.
Right now this information available in /proc/net/wireless.
That generalized method is not depending on driver implementation, 
driver just need to provide wireless statistics.

I found 2 places in kernel which report about RSSI to user space eventually.
First place, it's wlan_rndis driver base implementation 
./drivers/net/wireless/rndis_wlan.c.
The second place, it's mac80211 driver - beacon frame handling.

Unfortunately wireless driver we're using isn't rndis based and isn't 
mac80211 based.
We don't want to depends on driver code.

What community think in this situation, is it possible to add notifier 
with following responsibility:
     send netlink notification in case of signal level changed according 
to predefined by user threshold?

Technically it will looks like rndis_wlan approach - timer function with 
predefined frequency.

This functionality is needed to reduce user space daemon activity which 
provides information to GUI wifi indicator.
Also such approach could decrease time reaction on signal level changes. 
Currently, some OSes has 1 second interval,
another one has 3 seconds for checking RSSI.

-- 
Best regards,
Alexey Perevalov

Re: question about generalized way for RSSI notification

[Dan Williams]

On Fri, 2013-11-29 at 17:55 +0400, Alexey Perevalov wrote:
> Dear wireless subsystem maintainers,
> 
> I have a question regarding RSSI notification to the user space.
> Right now this information available in /proc/net/wireless.
> That generalized method is not depending on driver implementation, 
> driver just need to provide wireless statistics.
> 
> I found 2 places in kernel which report about RSSI to user space eventually.
> First place, it's wlan_rndis driver base implementation 
> ./drivers/net/wireless/rndis_wlan.c.
> The second place, it's mac80211 driver - beacon frame handling.

Do you mean ieee80211_rx_mgmt_beacon()?

> Unfortunately wireless driver we're using isn't rndis based and isn't 
> mac80211 based.
> We don't want to depends on driver code.

There's another possibility: use cfg80211 for the driver's configuration
interface.  cfg80211 is actually just some utility code that implements
the nl80211 API (which replaces the old WEXT configuration API).  Any
driver can use cfg80211, not just ones based on the mac80211 software
stack.  In fact, a number of the older "fullmac" drivers (libertas,
orinico) have been ported to use the cfg80211 API for all configuration
handling.

> What community think in this situation, is it possible to add notifier 
> with following responsibility:
>      send netlink notification in case of signal level changed according 
> to predefined by user threshold?

Look at net/wireless/nl80211.c; these are the entry points when
userspace is configuring the driver with nl80211 commands.  Userspace
would set up CQM thresholds with the NL80211_CMD_SET_CQM command, which
then gets passed to your driver.  Your driver could then set up a timer
or level triggers based on the userspace parameters, and then call
cfg80211_cqm_rssi_notify() as appropriate to send the notification to
userspace.

Dan

> Technically it will looks like rndis_wlan approach - timer function with 
> predefined frequency.
> 
> This functionality is needed to reduce user space daemon activity which 
> provides information to GUI wifi indicator.
> Also such approach could decrease time reaction on signal level changes. 
> Currently, some OSes has 1 second interval,
> another one has 3 seconds for checking RSSI.
> 

Re: question about generalized way for RSSI notification

[Alexey Perevalov]

Hi Dan,

Thank you very much, already existing netlink interface is really what 
we need.
And beacon frame it's better place to send notification about RSSI.


On 12/02/2013 07:15 PM, Dan Williams wrote:
> On Fri, 2013-11-29 at 17:55 +0400, Alexey Perevalov wrote:
>> Dear wireless subsystem maintainers,
>>
>> I have a question regarding RSSI notification to the user space.
>> Right now this information available in /proc/net/wireless.
>> That generalized method is not depending on driver implementation,
>> driver just need to provide wireless statistics.
>>
>> I found 2 places in kernel which report about RSSI to user space eventually.
>> First place, it's wlan_rndis driver base implementation
>> ./drivers/net/wireless/rndis_wlan.c.
>> The second place, it's mac80211 driver - beacon frame handling.
> Do you mean ieee80211_rx_mgmt_beacon()?
Yes I meant IEEE80211_STYPE_BEACON handling which use already existing 
netlink infrastructure.

>> Unfortunately wireless driver we're using isn't rndis based and isn't
>> mac80211 based.
>> We don't want to depends on driver code.
> There's another possibility: use cfg80211 for the driver's configuration
> interface.  cfg80211 is actually just some utility code that implements
> the nl80211 API (which replaces the old WEXT configuration API).  Any
> driver can use cfg80211, not just ones based on the mac80211 software
> stack.  In fact, a number of the older "fullmac" drivers (libertas,
> orinico) have been ported to use the cfg80211 API for all configuration
> handling.
>
>> What community think in this situation, is it possible to add notifier
>> with following responsibility:
>>       send netlink notification in case of signal level changed according
>> to predefined by user threshold?
> Look at net/wireless/nl80211.c; these are the entry points when
> userspace is configuring the driver with nl80211 commands.  Userspace
> would set up CQM thresholds with the NL80211_CMD_SET_CQM command, which
> then gets passed to your driver.  Your driver could then set up a timer
> or level triggers based on the userspace parameters, and then call
> cfg80211_cqm_rssi_notify() as appropriate to send the notification to
> userspace.
>
> Dan
>
>> Technically it will looks like rndis_wlan approach - timer function with
>> predefined frequency.
>>
>> This functionality is needed to reduce user space daemon activity which
>> provides information to GUI wifi indicator.
>> Also such approach could decrease time reaction on signal level changes.
>> Currently, some OSes has 1 second interval,
>> another one has 3 seconds for checking RSSI.
>>


-- 
Best regards,
Alexey Perevalov