linux-kernel - Re: [PATCH v2] staging: comedi: resolve section mismatch in s626

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Message-ID: <4F798416.8040709@mev.co.uk>
Date:	Mon, 2 Apr 2012 11:48:54 +0100
From:	Ian Abbott <abbotti@....co.uk>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Gerard Snitselaar <dev@...tselaar.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"fmhess@...rs.sourceforge.net" <fmhess@...rs.sourceforge.net>,
	Ian Abbott <ian.abbott@....co.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] staging: comedi: resolve section mismatch in s626

On 2012-03-19 23:26, Greg KH wrote:
> On Mon, Mar 19, 2012 at 03:46:49PM -0700, Gerard Snitselaar wrote:
>> On Mon, Mar 19, 2012 at 09:43:25AM -0700, Gerard Snitselaar wrote:
>>> On Mon, Mar 19, 2012 at 09:31:03AM -0700, Greg KH wrote:
>>>>
>>>> Ick, why is this loop even needed?  We are only here if the pci device
>>>> is present in the system so this shouldn't be needed at all, right?
>>>>
>>>> Or is this a bit more complex than I am making it out to be?
>>>>
>>>> greg k-h
>>>
>>> Most likely not. I will take a look at some of the other drivers in
>>> comedi and see how the attach code looks there. I believe the code
>>> section in hpdi_attach() was written by the same person. Unfortunately
>>> I don't have a device to actually play around and see what changes are
>>> doing.
>>>
>>
>> I looked at this a bit more. It looks like they lose visibility to the
>> pci_dev structure.
>>
>> *_probe()
>>     comedi_pci_auto_config()     pci_dev
>>        comedi_auto_config()      pci_dev->dev
>>           comedi_device_attach() ??
>>              driv->attach()      ??<= iterate through pci devices.
>>
>> Most of the examples I have looked at so far use for_each_pci_dev() to
>> find the device, and s626 shortcuts it a bit by directly making calls
>> to pci_get_subsys() with specific ids. They all verify they have the
>> right device by checking the bus and slot that are grabbed from the
>> pci_dev in comedi_pci_auto_config() and passed down.
>
> Ugh, surely there's a way to keep the pci dev through the
> comedi_device_attach() call, right?

comedi_device_attach() is also called for the COMEDI_DEVCONFIG ioctl for 
"manually" configuring a comedi device, and that has no idea about 
struct pci_dev, etc.

I recently posted a series of patches that allows lower-level comedi 
drivers to supply separate hooks for auto-configuring PCI devices or USB 
devices without abusing the old "manual configuration" code paths, see 
<http://driverdev.linuxdriverproject.org/pipermail/devel/2012-March/025331.html>.

The old loop that searches the PCI bus is still needed for the "manual 
configuration" code path.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
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