Subject: Re: Can we remove pci_find_device() yet?
From: Ben Hutchings <bhutchings@solarflare.com>
To: Krzysztof Halasa <khc@pm.waw.pl>
Cc: Greg KH <gregkh@suse.de>, Tilman Schmidt <tilman@imap.cc>,
       Stephen Rothwell <sfr@canb.auug.org.au>,
       LKML <linux-kernel@vger.kernel.org>, netdev@vger.kernel.org,
       Karsten Keil <isdn@linux-pingi.de>, isdn4linux@listserv.isdn4linux.de
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Organization: Solarflare Communications
Date: Tue, 12 Jan 2010 20:53:25 +0000
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On Tue, 2010-01-12 at 21:34 +0100, Krzysztof Halasa wrote:
> Greg KH <gregkh@suse.de> writes:
> 
> > Close, but if you do this, please name the function
> > hisax_find_pci_device() or something, and change the drivers to use it
> > instead.  Also put a big fat warning in the function that calling this
> > is unsafe for any PCI hotplug type machine.
> 
> BTW, I have a driver in the works which uses these functions, and I
> wonder how to do it correctly. The problem is that the hardware is a
> dual-function PCI card (two DEC Tulip Ethernet controllers) but part of
> the first device (EEPROM interface or something like that) is used by
> both (there is an FPGA connected there, serving both channels).
> 
> This means drivers for dev#0 and dev#1 (both "normal" PCI controllers)
> need to register and access part of dev#0 BARs.

I hope you realise that this is a design error!  Linux is fairly
forgiving and allows PCI drivers to do unusual things, but other OSes
make it hard or impossible for PCI drivers to coordinate multiple
functions.

> How do I do that properly, in terms of PCI API?

One of our older controllers had a similar design error in that the two
functions would sometimes have to be reset together.  The way we look
for the second function is:

	dev = pci_dev_get(dev1);
	while ((dev = pci_get_device(vendor_id, device_id, dev))) {
		if (dev->bus == dev1->bus &&
		    dev->devfn == dev1->devfn + 1) {
			dev2 = dev;
			break;
		}
	}

I assume this is 'properly' since no-one has told me otherwise.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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