USB: Allow transfer_buffer with transfer_dma

[linux-2.6-omap-h63xx.git] / drivers / usb / core / message.c

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index da4ee07e0094c59d17e96166abe1ff346f23ea6b..b7434787db5fb312cb705545fbc4fa64ab9dfc0e 100644 (file)
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -412,10 +412,24 @@ int usb_sg_init (
                io->urbs [i]->status = -EINPROGRESS;
                io->urbs [i]->actual_length = 0;
 
+               /*
+                * Some systems need to revert to PIO when DMA is temporarily
+                * unavailable.  For their sakes, both transfer_buffer and
+                * transfer_dma are set when possible.  However this can only
+                * work on systems without HIGHMEM, since DMA buffers located
+                * in high memory are not directly addressable by the CPU for
+                * PIO ... so when HIGHMEM is in use, transfer_buffer is NULL
+                * to prevent stale pointers and to help spot bugs.
+                */
                if (dma) {
-                       /* hc may use _only_ transfer_dma */
                        io->urbs [i]->transfer_dma = sg_dma_address (sg + i);
                        len = sg_dma_len (sg + i);
+#ifdef CONFIG_HIGHMEM
+                       io->urbs[i]->transfer_buffer = NULL;
+#else
+                       io->urbs[i]->transfer_buffer =
+                               page_address(sg[i].page) + sg[i].offset;
+#endif
                } else {
                        /* hc may use _only_ transfer_buffer */
                        io->urbs [i]->transfer_buffer =