Re: ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally attached PHYs)

Christoph Hellwig
2005-10-21T18:06:23Z

On Fri, Oct 21, 2005 at 01:48:45PM -0400, Luben Tuikov wrote:
> > why James has suggested implementing SMP as a block driver. People get
> > stuck into thinking "block driver == block device", which is wrong. The

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> > Linux block layer is nothing but a message queueing interface.
>
> Now, just because James suggested implementing the SMP service as a block
> device you think this is the right thing to do?
>
> How about this: Why not as a char device?

you can implement a char device using the block layer. See
drivers/scsi/{ch.c,osst.c,sg.c,st.c} for examples.

That beeing said I tried this approach. It looks pretty cool when you
think about it, but the block layer is quite a bit too heavyweight for
queueing up a few SMP requests, and we need to carry too much useless
code around for it.