linux-kernel - Re: pci_get_device_reverse(), why does Calgary need this?

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Message-Id: <200802132320.37172.bzolnier@gmail.com>
Date:	Wed, 13 Feb 2008 23:20:36 +0100
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Greg KH <greg@...ah.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, muli@...ibm.com,
	jdmason@...zu.us, linux-ide@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, linux-kernel@...r.kernel.org,
	discuss@...-64.org
Subject: Re: pci_get_device_reverse(), why does Calgary need this?

On Wednesday 13 February 2008, Greg KH wrote:
> On Wed, Feb 13, 2008 at 09:28:24AM -0800, Greg KH wrote:
> > On Wed, Feb 13, 2008 at 01:34:12PM +0100, Bartlomiej Zolnierkiewicz wrote:
> > > On Wednesday 13 February 2008, Greg KH wrote:
> > > > On Wed, Feb 13, 2008 at 02:17:37AM +0000, Alan Cox wrote:
> > > > > > Why does the calgary driver need this?  Can we just use pci_get_device()
> > > > > > instead?  Why do you need to walk the device list backwards?  Do you get
> > > > > > false positives going forward?
> > > > > 
> > > > > It doesn't look to be performance critical so the driver can
> > > > > pci_get_device until the end and use the final hit anyway.
> > > > 
> > > > That would make more sense.
> > > > 
> > > > > IDE reverse is more problematic but nobody seems to use it.
> > > > 
> > > > I've seen two posters say they use it.  I'm wondering what it is really
> > > > solving if they use it, and why if it's really needed, scsi never had to
> > > > implement such a hack...
> > > 
> > > It is no longer solving anything, just adds more pain. ;)
> > > 
> > > [ The option comes from 2.2.x (so long before LABEL=/ and /dev/disk/by-id/
> > >   became popular).  Some "off-board" controllers integrated on motherboards
> > >   used to appear before "on-board" IDE on PCI bus so this option was meant
> > >   to preserve the legacy ordering. ]
> > > 
> > > Since it is valid only when "Probe IDE PCI devices in the PCI bus order
> > > (DEPRECATED)" config option is used it is already on its way out (though
> > > marking it as obsoleted would make it more explicit).
> > > 
> > > I think that removing "ide=reverse" in 2.6.26 would be OK...
> > 
> > Great, thanks for your blessing.  I'll make up a patch and send it to
> > you for approval.
> 
> How does the patch below look?  I didn't want to remove the whole config
> option, as there is more to the logic than just the "reverse order"
> stuff there.

looks fine,

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>

> If you don't mind, can I take this through the PCI tree so as to allow
> the removal of this pci function afterwards?

[...]

great, could you also:
- rebase it on top of the patch below
- forward the patch below to Linus for 2.6.25

?

From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Subject: [PATCH] ide: mark "ide=reverse" option as obsolete

- it is valid only if "Probe IDE PCI devices in the PCI bus order
  (DEPRECATED)" config option is used

- Greg needs to remove pci_get_device_reverse() for PCI core changes

Cc: Greg Kroah-Hartman <gregkh@...e.de>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
---
 drivers/ide/ide.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: b/drivers/ide/ide.c
===================================================================
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -1038,7 +1038,7 @@ static int __init ide_setup(char *s)
 	if (!strcmp(s, "ide=reverse")) {
 		ide_scan_direction = 1;
 		printk(" : Enabled support for IDE inverse scan order.\n");
-		return 1;
+		goto obsolete_option;
 	}
 #endif
 
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