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

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Message-ID: <20120410192252.GB4011@cantor.Home>
Date:	Tue, 10 Apr 2012 12:24:14 -0700
From:	Gerard Snitselaar <dev@...tselaar.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Ian Abbott <abbotti@....co.uk>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Ian Abbott <ian.abbott@....co.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"fmhess@...rs.sourceforge.net" <fmhess@...rs.sourceforge.net>
Subject: Re: [PATCH v2] staging: comedi: resolve section mismatch in s626

On Tue Apr 10 12, Greg KH wrote:
> On Mon, Apr 02, 2012 at 11:48:54AM +0100, Ian Abbott wrote:
> > 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.
> 
> So, now that I've applied your patches, this patch isn't needed anymore,
> right?  Or should it be reworked to use the new interfaces?
> 
> thanks,
> 
> greg k-h
> 

I'd say drop my patch and if there is still a mismatch problem it can
probably be resolved in a better way.

gerard

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