Re: [RFC][PATCH 1/4] PCI legacy I/O port free driver - Introduce pci_set_bar_mask*()

[Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>]

Russell King wrote:
> On Wed, Feb 15, 2006 at 03:03:56PM +0900, Kenji Kaneshige wrote:
> 
>>Andrew Morton wrote:
>>
>>>Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com> wrote:
>>>
>>>
>>>>This patch introduces a new interface pci_select_resource() for PCI
>>>>device drivers to tell kernel what resources they want to use.
>>>
>>>
>>>It'd be nice if we didn't need to introduce any new API functions for this.
>>>If we could just do:
>>>
>>>struct pci_something pci_something_table[] = {
>>>	...
>>>	{
>>>		...
>>>		.dont_allocate_io_space = 1,
>>>		...
>>>	},
>>>	...
>>>};
>>>
>>>within each driver which wants it.
>>>
>>>But I can't think of a suitable per-device-id structure with which we can
>>>do that :(
>>>
>>>
>>
>>My another idea was to use pci quirks. In this approach, we don't
>>need to introduce any new API. But I gave up this idea because it
>>looked abuse of pci quirks.
>>
>>Anyway, I try to think about new ideas we don't need to introduce
>>any new API.
> 
> 
> What about pci_enable_device_bars() ?
> 

Yes, it's one option (In fact, my first idea was using it),
though we need to move the following lines into
pci_enable_device_bars() from pci_enable_device().

        pci_fixup_device(pci_fixup_enable, dev);
        dev->is_enabled = 1;

Actually, IIRC, there are one or two existing drivers using it.
In addition to pci_enable_device_bars(), we can use
pci_request_region() for requesting each region instead of using
pci_request_regions().

The reason I didn't use this option was I thought we would need
bigger changes to drivers if we use pci_enable_devie_bars() and
pci_request_region(). For example, if we use pci_request_region()
for requesting the specific regions and if an error occurs
while doing that, we need to release only the regions we succeeded
in requesting. I think this is a little bit troublesome for driver
writers. In adition, though this is my personal opinion, only one
API to enable devices (e.g. pci_enable_device()) looks nice to me.
Anyway, I think it would be nice if we can solve the problem by
as small changes as possible to the existing drivers.
How do you think?

Thanks,
Kenji Kaneshige