Re: [PATCH v11 3/5] PCI: Move pci_clear_and_set_dword() helper to PCI header

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Nov 27, 2023 at 09:34:05AM +0800, Shuai Xue wrote:
> On 2023/11/22 21:14, Ilpo Järvinen wrote:
> > On Tue, 21 Nov 2023, Shuai Xue wrote:
> > 
> >> The clear and set pattern is commonly used for accessing PCI config,
> >> move the helper pci_clear_and_set_dword() from aspm.c into PCI header.
> >> In addition, rename to pci_clear_and_set_config_dword() to retain the
> >> "config" information and match the other accessors.
> >>
> >> No functional change intended.
> >>
> >> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> >> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> >> Tested-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
> >> ---
> >>  drivers/pci/access.c    | 12 ++++++++
> >>  drivers/pci/pcie/aspm.c | 65 +++++++++++++++++++----------------------
> >>  include/linux/pci.h     |  2 ++
> >>  3 files changed, 44 insertions(+), 35 deletions(-)
> >>
> >> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> >> index 6554a2e89d36..6449056b57dd 100644
> >> --- a/drivers/pci/access.c
> >> +++ b/drivers/pci/access.c
> >> @@ -598,3 +598,15 @@ int pci_write_config_dword(const struct pci_dev *dev, int where,
> >>  	return pci_bus_write_config_dword(dev->bus, dev->devfn, where, val);
> >>  }
> >>  EXPORT_SYMBOL(pci_write_config_dword);
> >> +
> >> +void pci_clear_and_set_config_dword(const struct pci_dev *dev, int pos,
> >> +				    u32 clear, u32 set)
> > 
> > Just noting that annoyingly the ordering within the name is inconsistent 
> > between:
> >   pci_clear_and_set_config_dword()
> > and
> >   pcie_capability_clear_and_set_dword()
> > 
> > And if changed, it would be again annoyingly inconsistent with 
> > pci_read/write_config_*(), oh well... And renaming pci_read/write_config_* 
> > into the hierarchical pci_config_read/write_*() form for would touch only 
> > ~6k lines... ;-D
> 
> I think it is a good question, but I don't have a clear answer. I don't
> know much about the name history.  As you mentioned, the above two
> accessors are the foundation operation, may it comes to @Bjorn decision.
> 
> The pci_clear_and_set_config_dword() is a variant of below pci accessors:
> 
>     pci_read_config_dword()
>     pci_write_config_dword()
> 
> At last, they are consistent :)

"pcie_capability_clear_and_set_dword" is specific to the PCIe
Capability, doesn't work for arbitrary config space, and doesn't
include the word "config".

"pci_clear_and_set_config_dword" seems consistent with the arbitrary
config space accessor pattern.

At least "clear_and_set" is consistent across both.

I'm not too bothered by the difference between "clear_and_set_dword"
(for the PCIe capability) and "clear_and_set_config_dword" (for
arbitrary things).

Yes, "pcie_capability_clear_and_set_config_dword" would be a little
more consistent, but seems excessively wordy (no pun intended).

But maybe I'm missing your point, Ilpo.  If so, what would you
propose?

Bjorn