Re: [PATCH RFC] pci: Make return value of pcie_capability_read*() consistent

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Apr 24, 2020 at 05:11:44PM +0800, Yicong Yang wrote:
> On 2020/4/24 14:02, Saheed Bolarinwa wrote:
> > On 4/24/20 12:38 AM, Bjorn Helgaas wrote:
> >> On Thu, Apr 23, 2020 at 07:55:17PM +0800, Yicong Yang wrote:

> >>> BTW, pci_{read, write}_config_*() may also have the issues that
> >>> export the private err code outside. You may want to solve these in
> >>> a series along with this patch.
> >>
> >> If you see a specific issue, please point it out.
> 
> arch/x86/platform/intel/iosf_mbi.c, iosf_mbi_pci_read_mdr():
>         result = pci_read_config_dword(mbi_pdev, MBI_MDR_OFFSET, mdr);
>         if (result < 0)
>             goto fail_read;
>         return 0;
>     fail_read:
>         dev_err(&mbi_pdev->dev, "PCI config access failed with %d\n", result);
>         return result;

This is a problem in the caller, not in pci_read_config*().  This
caller is definitely broken, but fixing it is material for other
patches, not the current effort to align pcie_capability_read*() and
pci_read_config*().

> >> I looked at pci_read_config_word(), and it can return
> >> PCIBIOS_DEVICE_NOT_FOUND, PCIBIOS_BAD_REGISTER_NUMBER, or the return
> >> value from bus->ops->read().
> >>
> >> I looked at all the users of PCIBIOS_*.  There's really no interesting
> >> use of any of them except by pcibios_err_to_errno() and
> >> xen_pcibios_err_to_errno(), so I'm not sure it's even worth keeping
> >> them.
> 
> maybe we can mark them as deprecated. I can send a RFC one to do so.

Let's put this on a list for later.  I want to make sure this first
effort is successful before throwing more stuff into the mix.

Bjorn