linux-kernel - Re: [Xen-devel] [PATCH V3 1/2] Drivers/PCI: Export pcie_has

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Date:   Wed, 13 Dec 2017 14:46:57 -0600
From:   Govinda Tatti <Govinda.Tatti@...cle.COM>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     jgross@...e.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, JBeulich@...e.com,
        bhelgaas@...gle.com, xen-devel@...ts.xenproject.org,
        boris.ostrovsky@...cle.COM, roger.pau@...rix.com
Subject: Re: [Xen-devel] [PATCH V3 1/2] Drivers/PCI: Export pcie_has_flr()
 interface


>>>> -static bool pcie_has_flr(struct pci_dev *dev)
>>>> +bool pcie_has_flr(struct pci_dev *dev)
>>>>   {
>>>>   	u32 cap;
>>>> @@ -3882,6 +3882,7 @@ static bool pcie_has_flr(struct pci_dev *dev)
>>>>   	pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
>>>>   	return cap & PCI_EXP_DEVCAP_FLR;
>>>>   }
>>>> +EXPORT_SYMBOL_GPL(pcie_has_flr);
>>> I'd rather change pcie_flr() so you could *always* call it, and it
>>> would return 0, -ENOTTY, or whatever, based on whether FLR is
>>> supported.  Is that feasible?
>> Sure, I will add pcie_has_flr() logic inside pcie_flr() and return
>> appropriate
>> values as suggested by you. Do we still want to retain pcie_has_flr() and
>> its usage inside pci.c?.Otherwise, I will remove it and do required cleanup.
> If you can restructure the code and remove pcie_has_flr() while
> retaining the existing behavior of its callers, that would be great.
I checked the current usage of pcie_has_flr() and pcie_flr(). I have a 
couple
of questions or need some clarification.

1. pcie_has_flr() usage inside pci_probe_reset_function().

    This function is only calling pcie_has_flr() but not pcie_flr().
    Rest of the code is trying to do specific type of reset except 
pcie_flr().

         rc = pci_dev_specific_reset(dev, 1);
         if (rc != -ENOTTY)
                 return rc;
         if (pcie_has_flr(dev))
                 return 0;
         rc = pci_af_flr(dev, 1);
         if (rc != -ENOTTY)
                 return rc;

    In other-words, I can remove usage of pcie_has_flr() in all other places
    in pci.c except in above function.

2. W.r.t pcie_flr(), I am planning to return error code. Currently, the 
following
    file/modules are calling this function. My plan is to add a check 
for return
    code and print a WANRING message if return code is NON-ZERO. I hope 
this is
    sufficient for this patch.

    drivers/crypto/qat/qat_common/adf_aer.c
    drivers/infiniband/hw/hfi1/chip.c (2 places)
    drivers/net/ethernet/cavium/liquidio/lio_vf_main.c
    drivers/net/ethernet/intel/ixgbe/ixgbe_main.c (2 places)
    drivers/pci/quirks.c (2 places)

Cheers
GOVINDA