On Fri, 21 Aug 2009, David Vrabel wrote:
> The WHCI HCD will also support urbs with scatter-gather lists. Add a
> usb_bus field to indicated how many sg list elements are supported by
> the HCD.
>
> Save space in struct urb by adding a URB_HAS_SG flag and reusing
> transfer_buffer to point to a struct sg_table.
>
> Split usb_sg_init() into usb_sg_init_with_sg() and
> usb_sg_init_without_sg().
>
> + /*
> + * 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;
> + *
> + * - 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.
> + */
> + 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;
> + }
This code has since been changed. You need to copy the current code.
Have you checked whether these alterations will break usbmon?
Alan Stern
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