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authorPete Zaitcev <zaitcev@redhat.com>2009-06-11 08:40:39 -0600
committerGreg Kroah-Hartman <gregkh@suse.de>2009-09-23 06:46:19 -0700
commit81bf46f3034046c572714bdee1dc51beb3475082 (patch)
treeb1fbbefed67dbf9f6e76e1ce0a8efb2e573599cd /drivers/usb/core
parent4e9e92003529e5c7bb11281f7c2c9b3fe8858403 (diff)
USB: Let usb_sg_init to set transfer_buffer more often
This fix permits the "new" usbmon to access usb-storage's data buffer without DMA remapping tricks. It should be compatible with PIO controllers and not add any new crashes. Note that from now on PIO controllers and usbmon are uniform in their access pattern and if one crashes then the other will too. Hopefuly neither does. As a side effect, we get rid for #ifdefs, which were a little ugly. Signed-off-by: Pete Zaitcev <zaitcev@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/core')
-rw-r--r--drivers/usb/core/message.c32
1 files changed, 10 insertions, 22 deletions
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 9720e699f47..da718e84d58 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -459,35 +459,23 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
io->urbs[i]->context = io;
/*
- * 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:
+ * 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.
*
- * - HIGHMEM, since DMA buffers located in high memory
- * are not directly addressable by the CPU for PIO;
- *
- * - IOMMU, since dma_map_sg() is allowed to use an
- * IOMMU to make virtually discontiguous buffers be
- * "dma-contiguous" so that PIO and DMA need diferent
- * numbers of URBs.
- *
- * So when HIGHMEM or IOMMU are in use, transfer_buffer
- * is NULL to prevent stale pointers and to help spot
- * bugs.
+ * Note that if IOMMU coalescing occurred, we cannot
+ * trust sg_page anymore, so check if S/G list shrunk.
*/
+ if (io->nents == io->entries && !PageHighMem(sg_page(sg)))
+ io->urbs[i]->transfer_buffer = sg_virt(sg);
+ else
+ io->urbs[i]->transfer_buffer = NULL;
+
if (dma) {
io->urbs[i]->transfer_dma = sg_dma_address(sg);
len = sg_dma_len(sg);
-#if defined(CONFIG_HIGHMEM) || defined(CONFIG_GART_IOMMU)
- io->urbs[i]->transfer_buffer = NULL;
-#else
- io->urbs[i]->transfer_buffer = sg_virt(sg);
-#endif
} else {
/* hc may use _only_ transfer_buffer */
- io->urbs[i]->transfer_buffer = sg_virt(sg);
len = sg->length;
}