From: Oliver Neukum > Sent: 29 April 2019 14:38 > On Mo, 2019-04-29 at 13:31 +0000, David Laight wrote: > > From: Oliver Neukum > > > > > > + * USB has unusual scatter-gather requirements: the length of each > > > + * scatterlist element except the last must be divisible by the > > > + * Bulk maxpacket value. Fortunately this value is always a > > > + * power of 2. Inform the block layer about this requirement. > > > + */ > > > > That isn't the correct restriction for XHCI. > > It has its own perverse restrictions. > > I think they are all handled within the xhci driver. > > Yes, but that does not matter. You just cannot assume that only > XHCI will be used with UAS. In particular virtual drivers will > be used. True, but there is no need to enforce a 2k (IIRC) alignment for XHCI. Perhaps you need a different property from the controller. Even if you decide the code is 'good enough' (I don't know what the cost is of enforcing a 2k alignment instead of 512 bytes) the comment is just plain wrong. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
