firewire: ohci: 0 may be a valid DMA address

I was told that there are obscure architectures with non-coherent DMA
which may DMA-map to bus address 0.  We shall not use 0 as a magic
number of uninitialized bus address variables.

The packet->payload_length > 0 test cannot be used either (except in
at_context_queue_packet) because local requests are not DMA-mapped
regardless of payload_length.  Hence add a state flag to struct
fw_packet.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 418415564791..a71477541dc7 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -995,7 +995,8 @@ static int at_context_queue_packet(struct context *ctx,
                         packet->ack = RCODE_SEND_ERROR;
                         return -1;
                 }
-                packet->payload_bus = payload_bus;
+                packet->payload_bus     = payload_bus;
+                packet->payload_mapped  = true;
 
                 d[2].req_count    = cpu_to_le16(packet->payload_length);
                 d[2].data_address = cpu_to_le32(payload_bus);
@@ -1023,7 +1024,7 @@ static int at_context_queue_packet(struct context *ctx,
          */
         if (ohci->generation != packet->generation ||
             reg_read(ohci, OHCI1394_IntEventSet) & OHCI1394_busReset) {
-                if (packet->payload_length > 0)
+                if (packet->payload_mapped)
                         dma_unmap_single(ohci->card.device, payload_bus,
                                          packet->payload_length, DMA_TO_DEVICE);
                 packet->ack = RCODE_GENERATION;
@@ -1059,7 +1060,7 @@ static int handle_at_packet(struct context *context,
                 /* This packet was cancelled, just continue. */
                 return 1;
 
-        if (packet->payload_bus)
+        if (packet->payload_mapped)
                 dma_unmap_single(ohci->card.device, packet->payload_bus,
                                  packet->payload_length, DMA_TO_DEVICE);
 
@@ -1723,7 +1724,7 @@ static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
         if (packet->ack != 0)
                 goto out;
 
-        if (packet->payload_bus)
+        if (packet->payload_mapped)
                 dma_unmap_single(ohci->card.device, packet->payload_bus,
                                  packet->payload_length, DMA_TO_DEVICE);