Hi Arnd,
On Mon, May 19, 2014 at 10:33 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Sunday 18 May 2014 19:38:45 Srikanth Thokala wrote:
>> +
>> + if (cfg->ops->is_valid_cfg_access) {
>> + if (!cfg->ops->is_valid_cfg_access(bus, devfn)) {
>> + *val = PCI_CFG_INVALID_DEVFN;
>> + return PCIBIOS_DEVICE_NOT_FOUND;
>> + }
>> + }
>
> Can you explain why this callback is needed? If the space for the
> bus is mapped, any access should just work.
As I was explaining to Will, there are some controllers which doesn't
return FF's
when a device is not found on the bus (as per the PCI specification) and
accessing such a device address from the kernel results in an external abort.
So, I added this additional logic in my driver to bypass this and
return FF's. Our IP
and even other controllers like Tegra, Renesas have similar implementation.
We cant think of a better solution and please let you us know if you
have any inputs.
Thanks
Srikanth
>
>> +
>> +/* Generic PCI CAM/ECAM Configuration Bus Operations */
>> +
>> +struct pci_cfg_bus_ops pci_cfg_cam_bus_ops = {
>> + .bus_shift = PCI_CFG_CAM_BUS_NUM,
>> + .map_bus = pci_cfg_map_bus_cam,
>> +};
>> +EXPORT_SYMBOL_GPL(pci_cfg_cam_bus_ops);
>> +
>> +struct pci_cfg_bus_ops pci_cfg_ecam_bus_ops = {
>> + .bus_shift = PCI_CFG_ECAM_BUS_NUM,
>> + .map_bus = pci_cfg_map_bus_ecam,
>> +};
>> +EXPORT_SYMBOL_GPL(pci_cfg_ecam_bus_ops);
>> +
>> +struct pci_ops pci_cfg_ops = {
>> + .read = pci_cfg_read,
>> + .write = pci_cfg_write,
>> +};
>> +EXPORT_SYMBOL_GPL(pci_cfg_ops);
>
>
> If we can find a way to remove the is_valid_cfg_access() check, we're
> probably better off removing the cfg_bus_ops as well, and exporting
> two sets of pci_ops. There will be a little more duplication here, but
> also less complexity in this module, and more importantly in the drivers
> using it.
>
> Arnd
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