b43: Rewrite DMA Tx status handling sanity checks

This rewrites the error handling policies in the TX status handler.
It tries to be error-tolerant as in "try hard to not crash the machine".
It won't recover from errors (that are bugs in the firmware or driver),
because that's impossible. However, it will return a more or less useful
error message and bail out. It also tries hard to use rate-limited messages
to not flood the syslog in case of a failure.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/dma.h

@@ -1,7 +1,7 @@
 #ifndef B43_DMA_H_
 #define B43_DMA_H_
 
-#include <linux/ieee80211.h>
+#include <linux/err.h>
 
 #include "b43.h"
 
@@ -164,6 +164,10 @@ struct b43_dmadesc_generic {
 #define B43_RXRING_SLOTS		64
 #define B43_DMA0_RX_BUFFERSIZE		IEEE80211_MAX_FRAME_LEN
 
+/* Pointer poison */
+#define B43_DMA_PTR_POISON		((void *)ERR_PTR(-ENOMEM))
+#define b43_dma_ptr_is_poisoned(ptr)	(unlikely((ptr) == B43_DMA_PTR_POISON))
+
 
 struct sk_buff;
 struct b43_private;