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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jeff Garzik <jeff@garzik.org>
Cc: Tejun Heo <htejun@gmail.com>,
	Linux IDE mailing list <linux-ide@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: devres and requesting resources
Date: Fri, 29 Feb 2008 13:55:56 +0000	[thread overview]
Message-ID: <20080229135556.6eafe4aa@core> (raw)
In-Reply-To: <47C7F664.5040102@garzik.org>

> Only rare PCI devices are shareable among multiple drivers.

Really. Let me see
	AGP & EDAC
	Serial/Parallel combo ports
	MPIIX
	CS5520
	Lots of I2C bus stuff
	VGA v 3D

There are quite a few, and some are already quite fun enough with our pci
struct model.

> sata_* at least intentionally used pci_request_regions() because it is 
> obvious from the hardware spec that multiple regions accessed by 
> multiple drivers is highly unlikely, without the driver being 
> specifically coded to support such sharing.  Such sharing code is far 
> beyond simple resource reservation, to avoid stepping on toes when there 
> is a single MMIO region and set of interrupt clearing registers.
> 
> So reading your email it sounds like there are valid cases for both 
> configurations.
> 
> Its a design choice either way, not a bug either way.

It is a flaw: devres that assumes it should grab all resources is unusable
for some other drivers - it is no longer generic and that makes it far
less useful. I've got no problem with the idea of a devres way to say
"and I want it all, mine mine mine" but that should not be the only
behaviour.

Alan

      parent reply	other threads:[~2008-02-29 14:07 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-29  0:36 Jeff Garzik
2008-02-29 11:26 ` Alan Cox
2008-02-29 12:11   ` Jeff Garzik
2008-02-29 12:28     ` Tejun Heo
2008-02-29 14:01       ` Alan Cox
2008-02-29 14:17         ` Tejun Heo
2008-02-29 19:25           ` Jeff Garzik
2008-02-29 17:04         ` Bartlomiej Zolnierkiewicz
2008-02-29 17:04           ` Alan Cox
2008-02-29 13:55     ` Alan Cox [this message]

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