sfc: Refactor struct efx_tx_buffer to use a flags field

Add a flags field to struct efx_tx_buffer, replacing the
continuation and map_single booleans.

Since a single descriptor cannot be both a TSO header and the last
descriptor for an skb, unionise efx_tx_buffer::{skb,tsoh} and add
flags for validity of these fields.

Clear all flags in free buffers (whereas previously the continuation
flag would be set).

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 14 insertions, 13 deletions

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index cd9c0a989692..0ac01fa6e63c 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -91,29 +91,30 @@ struct efx_special_buffer {
 };
 
 /**
- * struct efx_tx_buffer - An Efx TX buffer
- * @skb: The associated socket buffer.
- *      Set only on the final fragment of a packet; %NULL for all other
- *      fragments.  When this fragment completes, then we can free this
- *      skb.
- * @tsoh: The associated TSO header structure, or %NULL if this
- *      buffer is not a TSO header.
+ * struct efx_tx_buffer - buffer state for a TX descriptor
+ * @skb: When @flags & %EFX_TX_BUF_SKB, the associated socket buffer to be
+ *      freed when descriptor completes
+ * @tsoh: When @flags & %EFX_TX_BUF_TSOH, the associated TSO header structure.
  * @dma_addr: DMA address of the fragment.
+ * @flags: Flags for allocation and DMA mapping type
  * @len: Length of this fragment.
  *      This field is zero when the queue slot is empty.
- * @continuation: True if this fragment is not the end of a packet.
- * @unmap_single: True if dma_unmap_single should be used.
  * @unmap_len: Length of this fragment to unmap
  */
 struct efx_tx_buffer {
-        const struct sk_buff *skb;
-        struct efx_tso_header *tsoh;
+        union {
+                const struct sk_buff *skb;
+                struct efx_tso_header *tsoh;
+        };
         dma_addr_t dma_addr;
+        unsigned short flags;
         unsigned short len;
-        bool continuation;
-        bool unmap_single;
         unsigned short unmap_len;
 };
+#define EFX_TX_BUF_CONT         1       /* not last descriptor of packet */
+#define EFX_TX_BUF_SKB          2       /* buffer is last part of skb */
+#define EFX_TX_BUF_TSOH         4       /* buffer is TSO header */
+#define EFX_TX_BUF_MAP_SINGLE   8       /* buffer was mapped with dma_map_single() */
 
 /**
  * struct efx_tx_queue - An Efx TX queue