linux-kernel - Re: [RFC] pci_bus conversion to struct device

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Message-ID: <20070127161935.GB10427@parisc-linux.org>
Date:	Sat, 27 Jan 2007 09:19:35 -0700
From:	Matthew Wilcox <matthew@....cx>
To:	Greg KH <greg@...ah.com>
Cc:	Martin Mares <mj@....cz>, colpatch@...ibm.com,
	linux-kernel@...r.kernel.org, linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: [RFC] pci_bus conversion to struct device

On Thu, Jan 18, 2007 at 01:00:44AM -0800, Greg KH wrote:
> On Thu, Jan 18, 2007 at 09:14:06AM +0100, Martin Mares wrote:
> > Hello!
> > 
> > > I recommend we just delete the pci_bus class.  I don't think it serves
> > > any useful purpose.  The bridge can be inferred frmo the sysfs hierarchy
> > > (not to mention lspci will tell you).  The cpuaffinity file should be
> > > moved from the bus to the device -- it really doesn't make any sense to
> > > talk about which cpu a bus is affine to, only a device.
> > 
> > It doesn't seem to serve any useful purpose other than the affinity now,
> > but I still think that it conceptually belongs there, because it makes
> > sense to have per-bus attributes. For example, in the future we could
> > show data width and signalling speed.

Data width is kind of hard to figure out since it's negotiated per
transaction.  One could conceive of a device which only does 32-bit
transactions to some addresses, and 64-bit transactions to others.

What I've done in recent patches is make these kinds of attributes
available per slot.

> So, if it were to stay, where in the tree should it be?  Hanging off of
> the pci device that is the bridge?  Or just placing these files within
> the pci device directory itself, as it is the bridge.

/sys/bus/pci/busses ?

> There are also some "legacy io" binary sysfs files in these directories
> for those platforms that support it (#ifdef HAVE_PCI_LEGACY), and I'm
> guessing that there is some user for them out there, otherwise they
> would not have been added...
> 
> Hm, only ia64 enables that option.  Matthew, do you care about those
> files?

I think they were added for Altix ... not sure who uses them.  Maybe X?
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