From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> Subject: Re: RFC: SCSI Generic version 4 interface Date: Sun, 26 Nov 2006 01:02:20 +0900 > From: Douglas Gilbert <dougg@xxxxxxxxxx> > Subject: Re: RFC: SCSI Generic version 4 interface > Date: Tue, 21 Nov 2006 17:06:46 -0500 > > > FUJITA Tomonori wrote: > > > From: Douglas Gilbert <dougg@xxxxxxxxxx> > > > Subject: RFC: SCSI Generic version 4 interface > > > Date: Mon, 06 Nov 2006 16:47:30 -0500 > > > > > >> SCSI Generic version 4 interface structure > > >> ========================================== > > >> Version 1.1 > > >> > > >> Goals: > > > > > > (snip) > > > > > >> - same structure can be used for a synchronous (e.g. interruptible > > >> ioctl) or asynchronous (e.g. ioctl()/read() ) pass through. > > > > > > Can you provide details on "asynchronous" part? > > > > I was trying to keep away from the implementation details > > but various people have pushed for more details ... > > > > > > Well as you are aware, the sg driver uses a write(), > > poll_or_signal,read() sequence to do asynchronous IO > > in version 3 (and roughly the same model in version 2). > > > > That write() has always made me uneasy and it is accident > > prone. > > I think write and read interface works nicely (though it's accident > prone as you said). They enable user-space applications to easily send > and receive sg_io_v4 structures asynchronously in batches (v3 can't in > batches). As you know, the current bsg adopts this interface. > > Another possible interface that I prefer is to send and receive > sg_io_v4 structures via two ring buffers. One problem about using non ioctl interfaces (read/write, ring buffer, whatever) is iovec compat issue. If sg4 still supports iovec for data transfer, it needs compat stuff (like sg_build_iovec). And non ioctl interfaces with iovec need to do more nasty compat stuff (like drivrs/input/evdev.c does). So I think that it's great for sg v4 not to support the old data-transfer interfaces (iovec, dio, and indirect io). - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
