Date: Fri, 23 Feb 2007 12:50:27 +0000
From: Alan <alan@lxorguk.ukuu.org.uk>
To: Robert Hancock <hancockr@shaw.ca>
Cc: Jeff Garzik <jeff@garzik.org>, akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ACPI driver support for pata
Message-ID: <20070223125027.3f0a7f14@lxorguk.ukuu.org.uk>
In-Reply-To: <45DE3207.6020707@shaw.ca>
References: <fa.IjFXvdcBtWXV65pRZipPd0NVTOA@ifi.uio.no>
	<45DD2E12.6000705@shaw.ca>
	<45DD3F20.7050907@pobox.com>
	<20070222142439.50cff3e9@lxorguk.ukuu.org.uk>
	<45DDCEC4.7050208@garzik.org>
	<20070222182939.56d43a68@lxorguk.ukuu.org.uk>
	<45DE3207.6020707@shaw.ca>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1540
Lines: 35

> Couldn't be do this generically inside libata core somehow, i.e. try to 
> use ACPI to set the proper mode and fall back to the driver-specific 
> mode setting code if that didn't work? I think if we could do that it 

We want to use the native hebaviour first

> would solve a number of problems (i.e. we could prevent it from doing 
> this on SATA controllers which appear to be IDE based on the PCI ID, 
> like the NVIDIA SATA controllers, since the _GTM and _STM methods seem 
> to have undefined behavior on SATA). This would also eliminate the need 

We check this already. A PATA interface without GTM/STM and friends will
not be picked up by pata_acpi but passed on to ata_generic.

> for mkinitrd, people, etc. to know that they're supposed to be loading 
> this other pata_acpi driver instead, since any PATA driver could take 
> advantage of this feature.

The link order is set up so that we try things in a very specific
deliberate order

- Hardware specific driver (unless it deliberately punts to ACPI)
- ACPI driver using _GTM/_STM etc
- Generic PCI driver ("stay in the mode the BIOS set and pray")
- ISA register compatibility mode (PIO)

This is essentially the strategy used by the old IDE layer since way back
when (minus ACPI support) and has served us pretty well.

Alan
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/