[Fwd: [parisc-linux] Problems with raw interface.]

Stephen C. Tweedie sct@redhat.com
19 Sep 2003 17:34:04 +0100


On Thu, 2003-09-18 at 22:08, Alan Cox wrote:
> Might interest you since this is possibly showing raw has cache
> coherency issues with HPPA (which is basically software coherency only)

> -----Forwarded Message-----
> > From: "SUDARSANAN,RANJITH (HP-India,ex2)" <ranjith_sudarsanan@hp.com>
> > To: parisc-linux@lists.parisc-linux.org
> > Subject: [parisc-linux] Problems with raw interface.
> > Date: Fri, 19 Sep 2003 00:36:55 +0530

> >         I am developing a scsi disk exerciser and I am blocked on a
> > strange problem with the raw interface. When I use the block device
> > /dev/sda directly I am able to read and write from the disk properly.
> > But when I use the raw interface I get garbage. For instance please
> > look at the output below. I am reading the 1st sector of the disk,
> > which is the boot sector, When I use the block device /dev/sda I get
> > my expected output, whereas when I use the raw interface I get
> > garbage. Can any one explain? The machine I am using is an L Class. 

Do you _ever_ get valid output, or is raw always failing?  There may
well be a cache coherency point being missed.

The key places are rw_raw_dev(), where we set up the virtual address to
physical page mappings, and brw_kiovec(), where the actual physical page
IO is done.