Re: [PATCH 3/6] PCI legacy I/O port free driver (take2) - Add device_flagsinto pci_device_id

[Kenji Kaneshige]

Greg KH wrote:
> On Tue, Feb 21, 2006 at 07:09:08PM -0500, Jeff Garzik wrote:
>
> > Andi Kleen wrote:
> >
> > > On Tuesday 21 February 2006 22:55, Jeff Garzik wrote:
> > >
> > >
> > >
> > > > It doesn't matter how easily its added, it is the wrong place to add 
> > > > such things.
> > > >
> > > > This is what the various functions called during pci_driver::probe() do...
> > >
> > >
> > > The problem is that at least on the e1000 it only applies to some of the 
> > > many PCI-IDs it supports. So the original patch had an long ugly switch
> > > with PCI IDs to check it. I suggested to use driver_data for it then,
> > > but Kenji-San ended up with this new field.  I actually like the idea
> > > of the new field because it would allow to add such things very easily
> > > without adding lots of code.
> > >
> > > it's not an uncommon situation. e.g. consider driver A which supports
> > > a lot of PCI-IDs but MSI only works on a few of them. How do you
> > > handle this? Add an ugly switch that will bitrot? Or put all the 
> > > information into a single place which is the pci_device_id array.
> >
> > You do what tons of other drivers do, and indicate this via driver_data. 
> > An enumerated type in driver_data can be used to uniquely identify any 
> > device or set of devices.
> >
> > No need to add anything.
>
>
> Yes, I agree, use driver_data, it's simpler, and keeps the PCI core
> clean.
>
> thanks,
>
> greg k-h

Hi,

Thank you very much for all of the comments.

The reason why I added the new field into struct pci_device_id is
as follows, though these are already explained completely by Andi.

   - By adding the new field instead of using driver_data, drivers
     can pass the flags to the kernel directly. That is, drivers
     don't need to call any new APIs to tell something to the kernel
     after checking their own driver_data in their .probe().

   - This new field can be used not only for ioport but also
     other purpose (e.g. MSI).

But according to the discussion, it doesn't look a good idea to add
the new field into pci_device_id this time. So I'll update my patches
to use the driver_data field instead.

Thanks,
Kenji Kaneshige
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