linux-kernel - Re: pci probe

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Message-ID: <20070516071851.GB19294@kroah.com>
Date:	Wed, 16 May 2007 00:18:51 -0700
From:	Greg KH <greg@...ah.com>
To:	Manu Abraham <abraham.manu@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: pci probe

On Tue, May 15, 2007 at 05:15:28PM +0400, Manu Abraham wrote:
> Manu Abraham wrote:
> > Hi,
> > 
> > I do have a device that's a multifunction device. Eventhough a MFD, it
> > just has one Interrupt which is shared by by a Configuration space for
> > each function. ie, INTA is shared between them functions.
> > 
> > In such a case, i am wondering, (since pci_probe returns a pointer to
> > one PCI function alone and i need to use both the functions in one
> > module alone rather than using a module for each function and that the
> > functions are quite similar for them to be used in different modules,
> > such that a separate probe/ISR etc is used) whether using pci_get_device
> > would be a better alternative to do manual searching for the functions
> > in such a case.
> > 
> 
> Just figured out that pci_get_subsys() does work in a better. Looking at
> kernel sources all i find is just one single user of pci_get_subsys()
> 
> building the code around pci_get_subsys(), does this have any negative
> impact ?

Yes:
	- your device will not show up properly in sysfs (no
	  device/driver binding ability from userspace, no good
	  information so that udev can properly name the device, etc.)
	- your driver will not work on any pci-hotplug type system (that
	  includes expresscard and pccard and lots of high-end servers.
	- your driver will not be notified if the system is being
	  suspended or resumed or wanting to drop into a low power
	  state.
	- another driver can bind to your device without you ever
	  knowing it.

So in short, use pci_probe and just handle the fact that you need to be
called for two PCI devices and bind to both of them.  It shouldn't be
that hard...

thanks,

greg k-h
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