[Stgt-devel] Question for pass-through target design

[Robert Jennings]

It looks like the pass-through target support is currently broken, at
least as I've checked for ibmvstgt, but I think it's a general problem.
I wanted to check my assumptions and get ideas.

The code isn't allocating any memory to pass along to the sg code to store
the result of a read or data for a write.  Currently, dxferp for sg_io_hdr
or dout_xferp/din_xferp for sg_io_v4 are assigned to the value of uaddr,
which is set to 0 in kern_queue_cmd.  With the pointer set to NULL,
the pass-through target isn't going to function.  Even if we had memory
allocated, there isn't a means of getting data to be written via sg down
this code path.

What ideas are there as to how the data will get to user-space so that
we can use sg?

Regards,
Robert Jennings