USB adapter firmware: 1.8.x generates lots of TX EXC events?

Jouni Malinen jkmaline
Sat Jun 11 21:12:03 PDT 2005

On Sat, Jun 11, 2005 at 09:22:23PM +0100, Chris Rankin wrote:

> I've noticed that linux-wlan-ng's prism2_usb driver has great difficulty talking to a hostap AP
> device, whenver the USB adapter is running firmware 1.8.x. The reason for this seems to be that
> the AP receives lots of TX EXC frames from the adapter, which the AP then responds to by lowering
> the bit rate. (More precisely, the hostap_sta_tx_exc_tasklet() function is invoked heavily when
> receiving frames from a 1.8.x USB adapter, and hardly ever when the adapter runs <= 1.7.6.)

This would mean that the AP is not receiving acknowledgement frames from
the client.

> I remember that there is line of code in prism2_usb's hfa384x_drvr_txframe() function:
>         txdesc.tx_control =
>                 HFA384x_TX_MACPORT_SET(0) | HFA384x_TX_STRUCTYPE_SET(1) |
>                 HFA384x_TX_TXEX_SET(0) | HFA384x_TX_TXOK_SET(0);
> However, this says that we are already NOT transmitting either TXEX and TXOK frames. And IIRC, the
> adapter will lock up if we do enable them. So can anyone explain what firmware 1.8.x might be
> doing to trigger hostap's tx_exc tasklet, please?

I'm not completely sure I understood what you are saying here. There are
no "TXEX or TXOK frames" that the device would be sending. This is just
letting the firmware now that prism2_usb does not want to receive TxExc
or TxOk events. This is all internal to the client side and should not
have anything to do with AP reporting TxExc events (no ack received).
Either the client is not sending ack frames correctly or the AP is not
receiving them.

Jouni Malinen                                            PGP id EFC895FA

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