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

[Ian Abbott]

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.

The new comedi_driver->attach_pci() hook should be implemented for this
driver as well, and it's on my "todo" list (in my head!).

--
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@xxxxxxxxx>             )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587              )=-
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/