* Alan Stern <[EMAIL PROTECTED]> [070329 16:14]:
> On Thu, 29 Mar 2007, Tony Lindgren wrote:
>
> You left out part of my suggestion (setting the pointer to NULL):
>
> > > > +#ifndef CONFIG_HIGHMEM
> > > > io->urbs [i]->transfer_buffer =
> > > > page_address (sg [i].page) + sg
> > > > [i].offset;
> > >
> > > Insert here:
> > >
> > > +#else
> > > + io->urbs[i]->transfer_buffer = NULL;
>
> ^^^ You didn't do this.
>
> > >
> > > > +#endif
> > > > + } else {
> > > > len = sg [i].length;
> > > > + io->urbs [i]->transfer_buffer =
> > > > + page_address (sg [i].page) + sg
> > > > [i].offset;
> > > > }
Sorry I missed that, here's one more version.
Looks like I had some strangeness connecting to SMTP server, please
ignore similar copy this same message if it got sent..
Tony
From: Tony Lindgren <[EMAIL PROTECTED]>
Subject: USB: Allow transfer_buffer with transfer_dma
In case a DMA channel for an endpoint is temporarily
unavailable, some host controller drivers may still be
able to transfer the data using PIO. Without this patch
the transfer_buffer is not mapped, and host controller
does not know what to use for PIO.
Signed-off-by: Tony Lindgren <[EMAIL PROTECTED]>
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -412,15 +412,30 @@ int usb_sg_init (
io->urbs [i]->status = -EINPROGRESS;
io->urbs [i]->actual_length = 0;
+ /*
+ * Some systems can revert to PIO if DMA is temporarily
+ * unavailable; for their sake both transfer_buffer and
+ * transfer_dma must be set properly. However this is
+ * possible only on systems with no high memory, since
+ * DMA buffers located in high memory are not directly
+ * addressable by the kernel for PIO. When high memory
+ * is available, we NULL out transfer_buffer to avoid
+ * keeping a stale pointer and to help spot possible
+ * addressing 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);
+ io->urbs[i]->transfer_dma = sg_dma_address(sg + i);
+ len = sg_dma_len(sg + i);
+#ifndef CONFIG_HIGHMEM
+ io->urbs[i]->transfer_buffer =
+ page_address(sg[i].page) + sg[i].offset;
+#else
+ io->urbs[i]->transfer_buffer = NULL;
+#endif
} else {
- /* hc may use _only_ transfer_buffer */
- io->urbs [i]->transfer_buffer =
- page_address (sg [i].page) + sg [i].offset;
- len = sg [i].length;
+ len = sg[i].length;
+ io->urbs[i]->transfer_buffer =
+ page_address(sg[i].page) + sg[i].offset;
}
if (length) {
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