From: Helmut Schaa <helmut.schaa@googlemail.com>
To: Julian Calaby <julian.calaby@gmail.com>
Subject: Re: [PATCH 1/2] rt2x00: Write the frame *after* padding (rt2800 usb devices)
Date: Mon, 20 Dec 2010 11:30:22 +0100
Cc: Ismael Luceno <ismael.luceno@gmail.com>,
	"linux-wireless" <linux-wireless@vger.kernel.org>,
	Ivo Van Doorn <ivdoorn@gmail.com>,
	Gertjan van Wingerde <gwingerde@gmail.com>
References: <1292833909-20138-1-git-send-email-ismael.luceno@gmail.com> <201012200955.22087.helmut.schaa@googlemail.com> <AANLkTi=0AkWAoNhgMbkjwQb5Byu6SVWmOaNWRYsacfU6@mail.gmail.com>
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Am Montag, 20. Dezember 2010 schrieb Julian Calaby:
> On Mon, Dec 20, 2010 at 19:55, Helmut Schaa <helmut.schaa@googlemail.com> wrote:
> > Hi,
> >
> > Am Montag, 20. Dezember 2010 schrieb Ismael Luceno:
> >> Signed-off-by: Ismael Luceno <ismael.luceno@gmail.com>
> >> ---
> >>  drivers/net/wireless/rt2x00/rt2800usb.c |    7 ++++---
> >>  1 files changed, 4 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/net/wireless/rt2x00/rt2800usb.c b/drivers/net/wireless/rt2x00/rt2800usb.c
> >> index 3e0205d..85185de 100644
> >> --- a/drivers/net/wireless/rt2x00/rt2800usb.c
> >> +++ b/drivers/net/wireless/rt2x00/rt2800usb.c
> >> @@ -378,9 +378,10 @@ static void rt2800usb_write_tx_data(struct queue_entry *entry,
> >>        * | TXINFO | TXWI | 802.11 header | L2 pad | payload | pad | USB end pad |
> >>        *                 |<------------- tx_pkt_len ------------->|
> >>        */
> >> -        rt2800_write_tx_data(entry, txdesc);
> >> -        padding_len = roundup(entry->skb->len + 4, 4) - entry->skb->len;
> >> -        memset(skb_put(entry->skb, padding_len), 0, padding_len);
> >> +     padding_len = roundup(entry->skb->len + 4, 4) - entry->skb->len;
> >> +     memset(skb_put(entry->skb, padding_len), 0, padding_len);
> >> +
> >> +     rt2800_write_tx_data(entry, txdesc);
> >
> > Could you please explain this change in more detail please?
> > Why is it needed? rt2800_write_tx_data only adds the TXWI to the front of the
> > buffer, doing that before or after the padding doesn't make a difference, no?
> 
> Semantically it makes more sense this way, why modify a entry before
> writing it - but maybe the issue is that the name of the function
> makes it's function ambiguous, maybe renaming it to something along
> the lines of "rt2800_prepend_TXWI" would make it's purpose clearer.

Correct.

Helmut