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

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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@xxxxxxxxx>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
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