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

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Date:   Mon, 11 Dec 2017 18:59:19 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Govinda Tatti <Govinda.Tatti@...cle.COM>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, bhelgaas@...gle.com,
        boris.ostrovsky@...cle.COM, jgross@...e.com, JBeulich@...e.com,
        roger.pau@...rix.com, konrad.wilk@...cle.COM
Subject: Re: [PATCH V3 1/2] Drivers/PCI: Export pcie_has_flr() interface

On Mon, Dec 11, 2017 at 06:29:29PM -0600, Govinda Tatti wrote:
> 
> Thanks Bjorn for your review comments. Please see below for my comments.
> 
> On 12/8/2017 2:24 PM, Bjorn Helgaas wrote:
> >On Thu, Dec 07, 2017 at 05:21:44PM -0500, Govinda Tatti wrote:
> >>This patch exports pcie_has_flr() and it is being used by Xen pciback
> >>driver to reset (flr/slot/bus) PCI devices based on 'reset' SysFS
> >>attribute.
> >>
> >>Signed-off-by: Govinda Tatti <Govinda.Tatti@...cle.COM>
> >>---
> >>v3: -New
> >>
> >>  drivers/pci/pci.c   | 3 ++-
> >>  include/linux/pci.h | 1 +
> >>  2 files changed, 3 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >>index 6078dfc..499e922 100644
> >>--- a/drivers/pci/pci.c
> >>+++ b/drivers/pci/pci.c
> >>@@ -3872,7 +3872,7 @@ static void pci_flr_wait(struct pci_dev *dev)
> >>   * Returns true if the device advertises support for PCIe function level
> >>   * resets.
> >>   */
> >>-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.

Bjorn