2015-03-02 17:40:44

by Florian Westphal

Subject: [PATCH RFC 05/14] drivers: wireless: ar5523: use container_of

Compile tested only due to lack of hw.

If we want to shrink skb->cb then we'd have to see about
reducing struct ieee80211_tx_info, which gets embedded inside
skb->cb[].

It provides a scratch space to be used by wireless drivers.
ar5523 uses the maximum space available today (40 bytes), but it seems
we don't need this -- data->skb pointer seems to always point back to the
skb whose cb buffer the data structure resides, iow, given a pointer to the
embedded control buffer we can infer the skb address.

Cc: [email protected]
Signed-off-by: Florian Westphal <[email protected]>
---
drivers/net/wireless/ath/ar5523/ar5523.c | 8 ++++----
drivers/net/wireless/ath/ar5523/ar5523.h | 1 -
2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/ath/ar5523/ar5523.c b/drivers/net/wireless/ath/ar5523/ar5523.c
index f920506..7410ac0 100644
--- a/drivers/net/wireless/ath/ar5523/ar5523.c
+++ b/drivers/net/wireless/ath/ar5523/ar5523.c
@@ -779,8 +779,6 @@ static void ar5523_tx(struct ieee80211_hw *hw,
ieee80211_stop_queues(hw);
}

- data->skb = skb;
-
spin_lock_irqsave(&ar->tx_data_list_lock, flags);
list_add_tail(&data->list, &ar->tx_queue_pending);
spin_unlock_irqrestore(&ar->tx_data_list_lock, flags);
@@ -817,10 +815,12 @@ static void ar5523_tx_work_locked(struct ar5523 *ar)
if (!data)
break;

- skb = data->skb;
+ txi = container_of((void *)data, struct ieee80211_tx_info, driver_data);
txqid = 0;
- txi = IEEE80211_SKB_CB(skb);
+
+ skb = container_of((void *) txi, struct sk_buff, cb);
paylen = skb->len;
+
urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb) {
ar5523_err(ar, "Failed to allocate TX urb\n");
diff --git a/drivers/net/wireless/ath/ar5523/ar5523.h b/drivers/net/wireless/ath/ar5523/ar5523.h
index 00c6fd3..9a322a6 100644
--- a/drivers/net/wireless/ath/ar5523/ar5523.h
+++ b/drivers/net/wireless/ath/ar5523/ar5523.h
@@ -74,7 +74,6 @@ struct ar5523_tx_cmd {
struct ar5523_tx_data {
struct list_head list;
struct ar5523 *ar;
- struct sk_buff *skb;
struct urb *urb;
};

--
2.0.5

2015-03-03 09:16:59

by Pontus Fuchs

Subject: Re: [PATCH RFC 05/14] drivers: wireless: ar5523: use container_of

On 2015-03-02 18:40, Florian Westphal wrote:
> Compile tested only due to lack of hw.
>
> If we want to shrink skb->cb then we'd have to see about
> reducing struct ieee80211_tx_info, which gets embedded inside
> skb->cb[].
>
> It provides a scratch space to be used by wireless drivers.
> ar5523 uses the maximum space available today (40 bytes), but it seems
> we don't need this -- data->skb pointer seems to always point back to the
> skb whose cb buffer the data structure resides, iow, given a pointer to the
> embedded control buffer we can infer the skb address.
>
> Cc: [email protected]
> Signed-off-by: Florian Westphal <[email protected]>

Tested-by: Pontus Fuchs <[email protected]>