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

[Hans Zhang]

On 2025/3/21 05:28, Bjorn Helgaas wrote:
> On Sat, Mar 15, 2025 at 08:06:52AM +0800, Hans Zhang wrote:
> > 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.
> >
> > I have already replied to an email, please help review whether it is
> > appropriate.
>
> URL to the email on lore.kernel.org?
>
> If you mean this:
> https://lore.kernel.org/r/3cadf8d5-c4d8-4941-ae2e-8b00ceb83a8f@xxxxxxx,
> just post it as a v3 patch with the usual commit log and motivation
> for the change, and it will automatically get picked up in patchwork
> so it doesn't get forgotten.
>
> Right now the urgency seems fairly low since (IIUC) it doesn't fix an
> existing bug in the upstream code.

Hi Bjorn,

Thanks your for reply. I will submit v3 patch.

Best regards,
Hans