Re: block layer sg, bsg

[Douglas Gilbert]

Jens Axboe wrote:
> On Wed, Aug 04 2004, Jeff Garzik wrote:
>
> > On Wed, Aug 04, 2004 at 08:44:29AM -0700, David S. Miller wrote:
> >
> > > Or use a more portable well-defined type which does not change
> > > size nor layout between 32-bit and 64-bit environments.
> >
> > IMO if this (the above) is not done, the interface needs work.
> >
> > For interfaces that replace ioctl(2) with read(2)/write(2), for passing
> > data structures to/from the kernel, Al has rightly suggested that these
> > structures be not only fixed size (as David described above), but also
> > fixed-endian.
>
>
> I completely agree with that, we need a different structure for other
> devices as well. Show me what you'd like for libata, for instance.

If a new structure with anything but 'S' (0x53) in the first 4
bytes was chosen then the bsg driver could handle the new
structure and sg_io_hdr.

For example:
struct bsg_io_hdr {
    int8_t interface_id[4];   /* [i] 'B' in each element (required) */
    uint8_t dxfer_direction;
    .............
};

SCSI commands are all big endian and that seems to work
fine. Could pointers be passed as 8 byte big endian
unsigned integers?

Doug Gilbert

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