Re: [PATCH v2] ath9k_htc: Fix beacon distribution in IBSS mode

[Bruno Randolf <br1@einfach.org>]

On Tue September 21 2010 16:28:09 Rajkumar Manoharan wrote:
> This patch ensures fair beacon distribution in IBSS mode
> by configuring proper CWmin based on slot time.
> 
> Signed-off-by: Rajkumar Manoharan <rmanoharan@atheros.com>
> ---
>  drivers/net/wireless/ath/ath9k/htc_drv_beacon.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_beacon.c
> b/drivers/net/wireless/ath/ath9k/htc_drv_beacon.c index bd1506e..1b72aa4
> 100644
> --- a/drivers/net/wireless/ath/ath9k/htc_drv_beacon.c
> +++ b/drivers/net/wireless/ath/ath9k/htc_drv_beacon.c
> @@ -235,7 +235,14 @@ void ath9k_htc_beaconq_config(struct ath9k_htc_priv
> *priv) ath9k_hw_get_txq_props(ah, qnum, &qi_be);
> 
>  	qi.tqi_aifs = qi_be.tqi_aifs;
> -	qi.tqi_cwmin = 4*qi_be.tqi_cwmin;
> +	/* For WIFI Beacon Distribution
> +	 * Long slot time  : 2x cwmin
> +	 * Short slot time : 4x cwmin
> +	 */
> +	if (ah->slottime == ATH9K_SLOT_TIME_20)
> +		qi.tqi_cwmin = 2*qi_be.tqi_cwmin;
> +	else
> +		qi.tqi_cwmin = 4*qi_be.tqi_cwmin;
>  	qi.tqi_cwmax = qi_be.tqi_cwmax;
> 
>  	if (!ath9k_hw_set_txq_props(ah, priv->beaconq, &qi)) {

i am wondering - how does this relate to what i read in IEEE802.11-2007:

   11.1.2.2 Beacon generation in an IBSS

   b) Calculate a random delay uniformly distributed in the range between zero
      and twice aCWmin × aSlotTime,

wouldn't that mean that cwmin for the beacon queue should be 0 and cwmax 
should be 2x cwmin * slot time?

if the beacon queue cwmin is higher than the best effort queue, it would mean 
that the best effort queue gets precedence over beacon transmissions. but we 
want beacons to get sent out in any case.

also, what is the rationale behind using the best effort queue as a reference 
for cwmin/cwmax?

bruno