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From: Jeff Garzik <jgarzik@pobox.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Christophe Lucas <c.lucas@ifrance.com>,
	kernel-janitors@lists.osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [KJ] [PATCH] drivers/char/watchdog/* : pci_request_regions
Date: Thu, 17 Feb 2005 18:49:12 +0000	[thread overview]
Message-ID: <4214E728.3030501@pobox.com> (raw)
In-Reply-To: <20050214151244.GF29917@parcelfarce.linux.theplanet.co.uk>

[-- Attachment #1: Type: text/plain, Size: 911 bytes --]

Matthew Wilcox wrote:
> On Mon, Feb 14, 2005 at 04:01:11PM +0100, Christophe Lucas wrote:
> 
>>If PCI request regions fails, then someone else is using the
>>hardware we wish to use. For that one case, calling
>>pci_disable_device() is rather rude.
>>See : http://www.ussg.iu.edu/hypermail/linux/kernel/0502.1/1061.html
> 
> 
> Actually, that isn't necessarily true.  If the request_regions call fails,
> that can mean there's a resource conflict.  If so, leaving the device
> enabled is the worst possible thing to do as we'll now have two devices
> trying to respond to the same io accesses.

Incorrect.  If request_region() fails, drivers are coded to _not_ touch 
the hardware.  That's the entire purpose of the whole charade: to avoid 
having two devices responding to the same io accesses.

If your driver is talking to the hardware after request_region() fails, 
it is BROKEN plain and simple.

	Jeff




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WARNING: multiple messages have this Message-ID (diff)
From: Jeff Garzik <jgarzik@pobox.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Christophe Lucas <c.lucas@ifrance.com>,
	kernel-janitors@lists.osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [KJ] [PATCH] drivers/char/watchdog/* : pci_request_regions
Date: Thu, 17 Feb 2005 13:49:12 -0500	[thread overview]
Message-ID: <4214E728.3030501@pobox.com> (raw)
In-Reply-To: <20050214151244.GF29917@parcelfarce.linux.theplanet.co.uk>

Matthew Wilcox wrote:
> On Mon, Feb 14, 2005 at 04:01:11PM +0100, Christophe Lucas wrote:
> 
>>If PCI request regions fails, then someone else is using the
>>hardware we wish to use. For that one case, calling
>>pci_disable_device() is rather rude.
>>See : http://www.ussg.iu.edu/hypermail/linux/kernel/0502.1/1061.html
> 
> 
> Actually, that isn't necessarily true.  If the request_regions call fails,
> that can mean there's a resource conflict.  If so, leaving the device
> enabled is the worst possible thing to do as we'll now have two devices
> trying to respond to the same io accesses.

Incorrect.  If request_region() fails, drivers are coded to _not_ touch 
the hardware.  That's the entire purpose of the whole charade: to avoid 
having two devices responding to the same io accesses.

If your driver is talking to the hardware after request_region() fails, 
it is BROKEN plain and simple.

	Jeff




  reply	other threads:[~2005-02-17 18:49 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-02-14 15:01 [KJ] [PATCH] drivers/char/watchdog/* : pci_request_regions Christophe Lucas
2005-02-14 15:10 ` Matthew Wilcox
2005-02-14 15:12 ` Matthew Wilcox
2005-02-14 15:12   ` Matthew Wilcox
2005-02-17 18:49   ` Jeff Garzik [this message]
2005-02-17 18:49     ` Jeff Garzik
2005-02-17 19:04     ` Matthew Wilcox
2005-02-17 19:04       ` Matthew Wilcox
2005-02-17 19:22       ` Jeff Garzik
2005-02-17 19:22         ` Jeff Garzik
2005-02-14 15:50 ` Christophe Lucas
2005-02-14 19:10 ` Greg KH

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