Re: /dev/sd*

From: Adrian Bunk
Date: Wed Aug 09 2006 - 18:16:40 EST

On Wed, Aug 09, 2006 at 11:01:43PM +0100, Alan Cox wrote:
> Ar Mer, 2006-08-09 am 23:21 +0200, ysgrifennodd Adrian Bunk:
> > It might be a bit out of the scope of this thread, but why do some many
> > subsystems use the /dev/sd* namespace?
> >
> > Real SCSI devices use it.
> > The USB mass storage driver uses it.
> USB storage is real SCSI.

Real SCSI for a developer, for a user it's USB.

And things become even more confusing considering that the drive might
show up as /dev/sda or /dev/uba depending on the driver used.

> > libata uses it.
> >
> > I'd expext SATA or PATA devices at /dev/hd* or perhaps at /dev/ata* -
> > but why are they at /dev/sd*?
> ATA uses the top half of the scsi stack so ends up using the top layer
> scsi drivers. Its probably more efficient than writing new driver
> clones, especially as non disk ATA is also real SCSI (or very close).

You are talking about kernel<->kernel and kernel<->hardware interfaces.

I'm more concerned about the kernel<->userspace interface.

> You can use /dev/ata if you want - its just a udev problem ;)

Or by adding some manual links if using a static /dev.

But I'm still not getting the point why the /dev/sd* namespace has to be

> Alan



"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

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