Re: [v2] PCI: cadence: Add configuration space capability search API

[Hans Zhang]

On 2025/3/15 04:31, Bjorn Helgaas wrote:
> On Fri, Mar 14, 2025 at 06:35:11PM +0530, Manivannan Sadhasivam wrote:
> > ...
>
> > Even though this patch is mostly for an out of tree controller
> > driver which is not going to be upstreamed, the patch itself is
> > serving some purpose. I really like to avoid the hardcoded offsets
> > wherever possible. So I'm in favor of this patch.
> >
> > However, these newly introduced functions are a duplicated version
> > of DWC functions. So we will end up with duplicated functions in
> > multiple places. I'd like them to be moved (both this and DWC) to
> > drivers/pci/pci.c if possible. The generic function
> > *_find_capability() can accept the controller specific readl/ readw
> > APIs and the controller specific private data.
>
> I agree, it would be really nice to share this code.
>
> It looks a little messy to deal with passing around pointers to
> controller read ops, and we'll still end up with a lot of duplicated
> code between __pci_find_next_cap() and __cdns_pcie_find_next_cap(),
> etc.
>
> Maybe someday we'll make a generic way to access non-PCI "config"
> space like this host controller space and PCIe RCRBs.
>
> Or if you add interfaces that accept read/write ops, maybe the
> existing pci_find_capability() etc could be refactored on top of them
> by passing in pci_bus_read_config_word() as the accessor.

Hi Bjorn,

I have already replied to an email, please help review whether it is 
appropriate.

Best regards,
Hans