linux-kernel - Re: [PATCH] pci: introduce an ioremap

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Message-ID: <20080927083500.26819bf1@infradead.org>
Date:	Sat, 27 Sep 2008 08:35:00 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Matthew Wilcox <matthew@....cx>
Cc:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: introduce an ioremap_pcibar(pdev, barnr) function

On Fri, 26 Sep 2008 20:56:14 -0600
Matthew Wilcox <matthew@....cx> wrote:

> On Fri, Sep 26, 2008 at 04:36:41PM -0700, Arjan van de Ven wrote:
> > A common thing in many PCI drivers is to ioremap() an entire bar.
> > This is a slightly fragile thing right now, needing both an address
> > and a size, and many driver writers do.. various things there.
> > 
> > This patch introduces an ioremap_pcibar() function taking just a
> > PCI device struct and the bar number as arguments, and figures this
> > all out itself, in one place. In addition, we can add various
> > sanity checks to this function (the patch already checks to make
> > sure that the bar in question really is a MEM bar; few to no
> > drivers do that sort of thing).
> 
> So we already have a pci_iomap() which takes a 'max' argument.  If you
> make 'max' -1, don't you get this same behaviour?

there are many ways to map a bar... I'm just arguing for providing a
really simple, hard-to-get-wrong, one which only takes a device and a
bar number.
The goal of my patch isn't to introduce new functionality per se
(although having the ability to add checks is nice and welcome), it's
mostly to provide a simple, hard-to-get-wrong interface.
Less chance to get it wrong -> less hard to diagnose bugs.



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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