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

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Message-ID: <20120418232824.GA9419@kroah.com>
Date:	Wed, 18 Apr 2012 16:28:24 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Ian Abbott <abbotti@....co.uk>
Cc:	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Gerard Snitselaar <dev@...tselaar.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 Thu, Apr 12, 2012 at 02:03:16PM +0100, Ian Abbott wrote:
> On 2012/04/10 07:24 PM, 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:
> >>>>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?
> 
> I think it's still needed as that the comedi_driver->attach() hook
> is still needed to support manual configuration by the
> COMEDI_DEVCONFIG ioctl, and the existing code really shouldn't be
> looking in s626_pci_table[] as it's tagged __devinitconst.
> 
> I never saw any mismatched section warnings when I compiled a
> linux-next kernel on my system with a full set of comedi drivers,
> even with CONFIG_DEBUG_SECTION_MISMATCH configured.  I'm not sure
> why not, unless it has something to do with me building the kernel
> with a separate build directory.

Yes, I don't see the mismatch either, so I'm not going to apply this
patch, sorry, as I don't see what it is trying to fix at all.

greg k-h
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