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

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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.

   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 <>.

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              )=-
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