virtio — archive

[PATCH] pci: missing documentation for dealing with 64 bit config fields

From: Cornelia Huck <[email protected]>
To: [email protected]
Date: Thu, 02 Apr 2015 09:02:00 -0000

On Wed, 1 Apr 2015 20:42:13 +0200 "Michael S. Tsirkin" <[email protected]> wrote: > pci spec says what width access to use for 32, 16 and 8 > bit fields, but does not explicitly say what to do for > 32 bit fields. As we have text that says driver must s/32/64/ > treat 64 bit accesses as non-atomic, this seems > to imply driver should always do two 32 bit wide accesses. > > Let's make this an explicit requirement, and require > devices to support this. > > VIRTIO-139 > > Signed-off-by: Michael S. Tsirkin <[email protected]> > --- > conformance.tex | 1 + > content.tex | 19 ++++++++++++++ ----- > 2 files changed, 15 insertions(+), 5 deletions(-) (...) > +For device configuration access, the driver MUST use 8-bit wide > +accesses for 8-bit wide fields, 16-bit wide and aligned accesses > +for 16-bit wide fields and 32-bit wide and aligned accesses for > +32-bit and 64-bit wide fields. For 64-bit fields, the driver MAY > +access each of the high and low 32-bit parts of the field > +independently. Doesn't the last sentence follow from "use 32-bit wide accesses" already?