From f46d53d0e9151ea9553361d2bf044ba555350e5f Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Sun, 29 Jun 2014 01:45:53 +0100 Subject: defxx: Remove an incorrectly inverted preprocessor conditional The RX handler of the driver has two paths switched between, depending on the size of the frame received, as determined by SKBUFF_RX_COPYBREAK. When a small frame is received, a new skb allocated has data space large enough to hold the incoming frame only, and data is copied there from the original skb whose buffer is returned to the DMA RX ring; in that case `rx_in_place' is 0. When a large frame is received, a new skb allocated has data space large enough to hold the largest frame possible, including the overhead for alignment, the receive status and padding, over 4.5kiB overall, and its buffer is placed on the DMA RX ring while the original buffer is passed up to the network stack avoiding the need to copy data; in that case `rx_in_place' is 1. However the latter scenario is only possible when dynamic buffers are used, as determined by DYNAMIC_BUFFERS, because otherwise the buffers used for the DMA RX ring are fixed at the time the interface is brought up. That leads to an observation that the preprocessor conditional around the `rx_in_place' check is inverted, the check only really matters when dynamic buffers are in use. It has gone unnoticed for many years since support for using dynamic buffers on the DMA RX ring was introduced in 2.1.40 -- because the only problem that results is in the case where `rx_in_place' is 1 frame data received is unnecessarily copied to the newly-allocated buffer, before the buffer placed on the the DMA receive RX and its contents ignored. Therefore the only symptom is some performance loss. Rather than flipping the condition though I decided to discard the conditional altogether -- in the case of static buffers `rx_in_place' is always 0 so GCC will optimise the C conditional away instead. Tested on a few DEFPA and DEFTA boards successfully using both small and large frames, both with DYNAMIC_BUFFERS defined and with the macro undefined. Signed-off-by: Maciej W. Rozycki Signed-off-by: David S. Miller --- drivers/net/fddi/defxx.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'drivers/net/fddi/defxx.c') diff --git a/drivers/net/fddi/defxx.c b/drivers/net/fddi/defxx.c index eb78203cd58e..052927be074b 100644 --- a/drivers/net/fddi/defxx.c +++ b/drivers/net/fddi/defxx.c @@ -3074,10 +3074,7 @@ static void dfx_rcv_queue_process( break; } else { -#ifndef DYNAMIC_BUFFERS - if (! rx_in_place) -#endif - { + if (!rx_in_place) { /* Receive buffer allocated, pass receive packet up */ skb_copy_to_linear_data(skb, -- cgit v1.2.3-59-g8ed1b From 1b037474d0c0b5ceb65bc809e3d8ac4497ee041b Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Sun, 29 Jun 2014 02:09:19 +0100 Subject: defxx: Fix !DYNAMIC_BUFFERS compilation warnings This fixes compilation warnings: drivers/net/fddi/defxx.c:294: warning: 'dfx_rcv_flush' declared inline after being called drivers/net/fddi/defxx.c:294: warning: previous declaration of 'dfx_rcv_flush' was here drivers/net/fddi/defxx.c:2854: warning: 'my_skb_align' defined but not used triggered when the driver is built with DYNAMIC_BUFFERS undefined. Code tested to work just fine with these changes and a few DEFPA and DEFTA boards. Signed-off-by: Maciej W. Rozycki Signed-off-by: David S. Miller --- drivers/net/fddi/defxx.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'drivers/net/fddi/defxx.c') diff --git a/drivers/net/fddi/defxx.c b/drivers/net/fddi/defxx.c index 052927be074b..2aa57270838f 100644 --- a/drivers/net/fddi/defxx.c +++ b/drivers/net/fddi/defxx.c @@ -291,7 +291,11 @@ static int dfx_hw_dma_uninit(DFX_board_t *bp, PI_UINT32 type); static int dfx_rcv_init(DFX_board_t *bp, int get_buffers); static void dfx_rcv_queue_process(DFX_board_t *bp); +#ifdef DYNAMIC_BUFFERS static void dfx_rcv_flush(DFX_board_t *bp); +#else +static inline void dfx_rcv_flush(DFX_board_t *bp) {} +#endif static netdev_tx_t dfx_xmt_queue_pkt(struct sk_buff *skb, struct net_device *dev); @@ -2849,7 +2853,7 @@ static int dfx_hw_dma_uninit(DFX_board_t *bp, PI_UINT32 type) * Align an sk_buff to a boundary power of 2 * */ - +#ifdef DYNAMIC_BUFFERS static void my_skb_align(struct sk_buff *skb, int n) { unsigned long x = (unsigned long)skb->data; @@ -2859,7 +2863,7 @@ static void my_skb_align(struct sk_buff *skb, int n) skb_reserve(skb, v - x); } - +#endif /* * ================ @@ -3450,10 +3454,6 @@ static void dfx_rcv_flush( DFX_board_t *bp ) } } -#else -static inline void dfx_rcv_flush( DFX_board_t *bp ) -{ -} #endif /* DYNAMIC_BUFFERS */ /* -- cgit v1.2.3-59-g8ed1b