linux-kernel - Re: pci probe

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Message-ID: <464AF932.9070008@gmail.com>
Date:	Wed, 16 May 2007 16:29:38 +0400
From:	Manu Abraham <abraham.manu@...il.com>
To:	Greg KH <greg@...ah.com>
CC:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: pci probe

Greg KH wrote:
> 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.)

This one sounds bad.

> 	- your driver will not work on any pci-hotplug type system (that
> 	  includes expresscard and pccard and lots of high-end servers.

This doesn't matter

> 	- 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.

These also sound bad.

> 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 for the explanation.

Do you mean to have two PCIID tables ? But then that does mean 2 modules
don't you ? (i thought probe would be called once per module) Or you
mean to say use PCI_ANY_ID in the table to match multiple devices and
then allow probe to return a list of devices ?

Thanks,
Manu

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