netdev - Re: rtlwifi/rtl8192cu AP mode broken with PS STA

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Date:   Tue, 06 Apr 2021 13:00:33 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Ping-Ke Shih <pkshih@...ltek.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Larry Finger <Larry.Finger@...inger.net>
Subject: Re: rtlwifi/rtl8192cu AP mode broken with PS STA

"Maciej S. Szmigiero" <mail@...iej.szmigiero.name> writes:

> On 29.03.2021 00:54, Maciej S. Szmigiero wrote:
>> Hi,
>>
>> It looks like rtlwifi/rtl8192cu AP mode is broken when a STA is using PS,
>> since the driver does not update its beacon to account for TIM changes,
>> so a station that is sleeping will never learn that it has packets
>> buffered at the AP.
>>
>> Looking at the code, the rtl8192cu driver implements neither the set_tim()
>> callback, nor does it explicitly update beacon data periodically, so it
>> has no way to learn that it had changed.
>>
>> This results in the AP mode being virtually unusable with STAs that do
>> PS and don't allow for it to be disabled (IoT devices, mobile phones,
>> etc.).
>>
>> I think the easiest fix here would be to implement set_tim() for example
>> the way rt2x00 driver does: queue a work or schedule a tasklet to update
>> the beacon data on the device.
>
> Are there any plans to fix this?
> The driver is listed as maintained by Ping-Ke.

Yeah, power save is hard and I'm not surprised that there are drivers
with broken power save mode support. If there's no fix available we
should stop supporting AP mode in the driver.

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