Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in dma-iommu

[Christoph Hellwig]

On Wed, Sep 09, 2020 at 09:43:09AM +0800, Lu Baolu wrote:
> +       /*
> +        * The Intel graphic device driver is used to assume that the
> returned
> +        * sg list is not combound. This blocks the efforts of converting
> the

This adds pointless overly long lines.

> +        * Intel IOMMU driver to dma-iommu api's. Add this quirk to make the
> +        * device driver work and should be removed once it's fixed in i915
> +        * driver.
> +        */
> +       if (dev_is_pci(dev) &&
> +           to_pci_dev(dev)->vendor == PCI_VENDOR_ID_INTEL &&
> +           (to_pci_dev(dev)->class >> 16) == PCI_BASE_CLASS_DISPLAY) {
> +               for_each_sg(sg, s, nents, i) {
> +                       unsigned int s_iova_off = sg_dma_address(s);
> +                       unsigned int s_length = sg_dma_len(s);
> +                       unsigned int s_iova_len = s->length;
> +
> +                       s->offset += s_iova_off;
> +                       s->length = s_length;
> +                       sg_dma_address(s) = dma_addr + s_iova_off;
> +                       sg_dma_len(s) = s_length;
> +                       dma_addr += s_iova_len;
> +               }
> +
> +               return nents;
> +       }

This wants an IS_ENABLED() check.  And probably a pr_once reminding
of the workaround.