On Thu, 13 Jun 2019, Christoph Hellwig wrote:

> On Wed, Jun 12, 2019 at 10:43:11AM -0400, Alan Stern wrote:
> > Would it be okay to rely on the assumption that USB block devices never 
> > have block size < 512?  (We could even add code to the driver to 
> > enforce this, although refusing to handle such devices at all might be 
> > worse than getting an occasional error.)
> 
> sd.c only supports a few specific sector size, and none of them is
> < 512 bytes:
> 
>       if (sector_size != 512 &&
>           sector_size != 1024 &&
>           sector_size != 2048 &&
>           sector_size != 4096) {
>               ...
>               sdkp->capacity = 0;

Great!  So all we have to do is fix vhci-hcd.  Then we can remove all 
the virt_boundary_mask stuff from usb-storage and uas entirely.

(I'm assuming wireless USB isn't a genuine issue.  As far as I know, it 
is pretty much abandoned at this point.)

Valentina and Shua: Adding SG support to vhci-hcd shouldn't be too
hard.  It ought to be possible even without changing the network
protocol.

Alan Stern

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

Reply via email to