Re: [PATCH] b43: Fix DMA TX bounce buffer copying

[Larry Finger <Larry.Finger@lwfinger.net>]

Michael Buesch wrote:
> b43 allocates a bouncebuffer, if the supplied TX skb is in an invalid
> memory range for DMA.
> However, this is broken in that it fails to copy over some metadata to the
> new skb.
> 
> This patch fixes three problems:
> * Failure to adjust the ieee80211_tx_info pointer to the new buffer.
>   This results in a kmemcheck warning.
> * Failure to copy the skb cb, which contains ieee80211_tx_info, to the new skb.
>   This results in breakage of various TX-status postprocessing (Rate control).
> * Failure to transfer the queue mapping.
>   This results in the wrong queue being stopped on saturation and can result in queue overflow.
> 
> Signed-off-by: Michael Buesch <mb@bu3sch.de>
> Tested-by: Christian Casteyde <casteyde.christian@free.fr>
> 
> ---
> 
> Thanks to Johannes for tracking down this hard to find bug and
> thanks to Christian for testing.
> 
> Larry, I think I remember you reported a strange rate control failure on
> one of your cards. Does this patch fix it?
> 
> b43legacy:
> Note that b43legacy has the same bug and also needs fixing.
> Is there a maintainer for b43legacy?

Michael,

There was not really a rate-control problem - just a difficulty with
the operator. I was making a transmit test, then interrogating the
rate from the same console. By that time, the rate was back to 1 Mb/s
for control messages. When I looped the transmit tests, and looked at
the rate in a separate console, the code was doing mostly what it
should. Mostly because the success rate for the LP PHY does not
satisfy the assumptions that mistrel makes. One gets a higher
throughput with a fixed rate, but that will improve as power control
is implemented.

There is no maintainer for b43legacy. I have ported your patch for b43
to legacy and I will be testing and submitting it.

Larry