IDE class driver with SATA controllers

IDE class driver with SATA controllers

[Andrew Chew]

In my perusal of the kernel code, I noticed that the IDE subsystem
handles IDE controllers at legacy IO ports if no other driver claims
them (albeit without DMA support).  I was wondering if it could be
extended to support SATA controllers 
that aren't mapped to legacy I/O ports.

I'm aware of the idex=base,ctl,irq kernel option, but I can't seem to
get this to work with my SATA controller (using ide6=base,ctl,irq).

The reason I'm asking is because it would seem like a good thing to have
SATA controllers that are broadly compatible with IDE to be usable
without having to modify the core kernel drivers.  This would at least
allow a user to perform a Linux install on a SATA drive even if that
kernel doesn't have explicit support for the SATA controller.  A
kernel/driver update can then take place after the install.

Also, are there plans for libata to take over the IDE class driver
functionality in the future?

Re: IDE class driver with SATA controllers

[Alan Cox]

On Maw, 2004-08-31 at 22:03, Andrew Chew wrote:
> In my perusal of the kernel code, I noticed that the IDE subsystem
> handles IDE controllers at legacy IO ports if no other driver claims
> them (albeit without DMA support).  I was wondering if it could be
> extended to support SATA controllers 
> that aren't mapped to legacy I/O ports.

Generally no. It depends how the SATA controller provides interfaces.
If it provides the standards based interface with BIOS configured DMA
and timings but has no other support then add it to pci/generic.c. If it
doesn't then it'll need a driver anyway.

Alan

Re: IDE class driver with SATA controllers

[Jeff Garzik]

Andrew Chew wrote:
> The reason I'm asking is because it would seem like a good thing to have
> SATA controllers that are broadly compatible with IDE to be usable
> without having to modify the core kernel drivers.  This would at least
> allow a user to perform a Linux install on a SATA drive even if that
> kernel doesn't have explicit support for the SATA controller.  A
> kernel/driver update can then take place after the install.
> 
> Also, are there plans for libata to take over the IDE class driver
> functionality in the future?


Once ATAPI is complete, then I will green-light PATA support in libata.

Since libata already supports the standard bmdma stuff, and can even 
work in PIO-only mode without DMA (or even without interrupts, in 100% 
polling mode), it is definitely possible to drive the hardware.

If you want to play, and don't care about lack of ATAPI support (i.e. 
just disks), then it is possible today to do this.  #define 
ATA_FORCE_PIO and play away :)

With regards to libata being the default, making that an _option_ is 
feasible, but we will probably default to the IDE driver for quite some 
time.  There are issues of /dev/hda versus /dev/sda, keeping existing 
user setups working, etc.

	Jeff

Re: IDE class driver with SATA controllers

[Julien Oster]

Quoting Jeff Garzik <jgarzik@pobox.com>:

Hello Jeff,

> With regards to libata being the default, making that an _option_ is 
> feasible, but we will probably default to the IDE driver for quite some 
> time.  There are issues of /dev/hda versus /dev/sda, keeping existing 
> user setups working, etc.

once there is reasonable support to indeed use libata as default,
we could just wrap a pass through IDE driver around, which allocates the
major numbers for /dev/hd* and just feeds everything to libata. Or are the
semantics too different?

Regards,
Julien


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RE: IDE class driver with SATA controllers

[Andrew Chew]

> Jeff Garzik wrote:
> If you want to play, and don't care about lack of ATAPI support (i.e. 
> just disks), then it is possible today to do this.  #define 
> ATA_FORCE_PIO and play away :)

I don't see ATA_FORCE_PIO anywhere in the linux-2.6.9-rc1-bk14 tree.  Am
I looking for the wrong #define?