[Query] Update mac80211 BSS info from cfg8011_bss_inform_frame when hw_scan is enabled

[Query] Update mac80211 BSS info from cfg8011_bss_inform_frame when hw_scan is enabled

[Krishna Chaitanya]

Hi,

For chip sets that set

IEEE80211_HW_CONNECTION_MONITOR
hw_scan

the hardware does the scan and maintains the
connection.

So some HW's might drop the probe responses and
beacons as they are not required by the mac80211.

In those scenarios, the rate control module minstrel_ht called from
prep_connection throws a warning (in rate_control_send_low)
because "supp_rates" is not set, since scan results are updated
 through "cfg8011_bss_inform_frame" which doesn't call
"ieee80211_bss_info_update'.

How do we handle such scenarios? Does the cfg80211 need to
update the bss information in mac80211?

-- 
Thanks,
Regards,
Chaitanya T K.

Re: [Query] Update mac80211 BSS info from cfg8011_bss_inform_frame when hw_scan is enabled

[Johannes Berg]

On Sat, 2013-11-16 at 01:19 +0530, Krishna Chaitanya wrote:

> In those scenarios, the rate control module minstrel_ht called from
> prep_connection throws a warning (in rate_control_send_low)
> because "supp_rates" is not set, since scan results are updated
>  through "cfg8011_bss_inform_frame" which doesn't call
> "ieee80211_bss_info_update'.
> 
> How do we handle such scenarios? Does the cfg80211 need to
> update the bss information in mac80211?

No. What are you smoking?

You're not supposed to even call cfg80211_bss_inform_frame() from a
mac80211-based driver. Just report the RX frame properly.

johannes

Re: [Query] Update mac80211 BSS info from cfg8011_bss_inform_frame when hw_scan is enabled

[Krishna Chaitanya]

On Sun, Nov 17, 2013 at 2:46 PM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Sat, 2013-11-16 at 01:19 +0530, Krishna Chaitanya wrote:
>
>> In those scenarios, the rate control module minstrel_ht called from
>> prep_connection throws a warning (in rate_control_send_low)
>> because "supp_rates" is not set, since scan results are updated
>>  through "cfg8011_bss_inform_frame" which doesn't call
>> "ieee80211_bss_info_update'.
>>
>> How do we handle such scenarios? Does the cfg80211 need to
>> update the bss information in mac80211?
>
> No. What are you smoking?
>
> You're not supposed to even call cfg80211_bss_inform_frame() from a
> mac80211-based driver. Just report the RX frame properly.
>
Ours is a partial Full MAC driver which still uses mac80211 but mostly with
offloads to HW.

With mac80211 + hw_scan if we just report the RX frames, then we are just
eliminating the SCAN SM from mac80211, is this just to reduce the host
cycles? (apart from speeding up the channel switch)

Re: [Query] Update mac80211 BSS info from cfg8011_bss_inform_frame when hw_scan is enabled

[Johannes Berg]

On Sun, 2013-11-17 at 18:43 +0530, Krishna Chaitanya wrote:

> > You're not supposed to even call cfg80211_bss_inform_frame() from a
> > mac80211-based driver. Just report the RX frame properly.

> Ours is a partial Full MAC driver which still uses mac80211 but mostly with
> offloads to HW.
> 
> With mac80211 + hw_scan if we just report the RX frames, then we are just
> eliminating the SCAN SM from mac80211, is this just to reduce the host
> cycles? (apart from speeding up the channel switch)

When you post the driver for upstream we can talk about it. I have no
interest in it otherwise - but

 (a) you can't call cfg80211 from the driver and then have cfg80211 call
mac80211
     - that's a gross layering violation
 (b) if you're offloading much, you're probably not using a lot of
mac80211 and
     should come with a proposal to refactor the code

johannes

Re: [Query] Update mac80211 BSS info from cfg8011_bss_inform_frame when hw_scan is enabled

[Krishna Chaitanya]

On Mon, Nov 18, 2013 at 6:31 PM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Sun, 2013-11-17 at 18:43 +0530, Krishna Chaitanya wrote:
>
>> > You're not supposed to even call cfg80211_bss_inform_frame() from a
>> > mac80211-based driver. Just report the RX frame properly.
>
>> Ours is a partial Full MAC driver which still uses mac80211 but mostly with
>> offloads to HW.
>>
>> With mac80211 + hw_scan if we just report the RX frames, then we are just
>> eliminating the SCAN SM from mac80211, is this just to reduce the host
>> cycles? (apart from speeding up the channel switch)
>
> When you post the driver for upstream we can talk about it. I have no
> interest in it otherwise - but
>
May not be possible.

>  (a) you can't call cfg80211 from the driver and then have cfg80211 call
> mac80211
>      - that's a gross layering violation
That was not my intention either.
>  (b) if you're offloading much, you're probably not using a lot of
> mac80211 and
>      should come with a proposal to refactor the code
If we want to truly offload the SCAN to HW then we should have some
way to update scan_results without ever sending the probe responses
and beacons up (saves lots of host cycles, assuming Connection
Monitoring is also offloaded).

For now, will change the driver to pass the beacons/probes up for
updating scan results.

Thanks.