linux-kernel - Re: [PATCH 1/4] PCI: introduce helper functions for device flag operation

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Date:	Mon, 28 Jul 2014 20:31:13 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	ethan zhao <ethan.zhao@...cle.com>
Cc:	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, gleb@...nel.org, pbonzini@...hat.com,
	kvm@...r.kernel.org, konrad.wilk@...cle.com,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	xen-devel@...ts.xenproject.org, alexander.h.duyck@...el.com,
	ethan.kernel@...il.com
Subject: Re: [PATCH 1/4] PCI: introduce helper functions for device flag
 operation

On Tue, 2014-07-29 at 09:53 +0800, ethan zhao wrote:
> On 2014/7/29 5:00, Alex Williamson wrote:
> > On Wed, 2014-07-23 at 00:19 +0800, Ethan Zhao wrote:
> >> This patch introduced three helper functions to hide direct
> >> device flag operation.
> >>
> >> void pci_set_dev_assigned(struct pci_dev *pdev);
> >> void pci_set_dev_deassigned(struct pci_dev *pdev);
> >> bool pci_is_dev_assigned(struct pci_dev *pdev);
> >>
> >> Signed-off-by: Ethan Zhao <ethan.zhao@...cle.com>
> >> ---
> >>   include/linux/pci.h |   13 +++++++++++++
> >>   1 files changed, 13 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/include/linux/pci.h b/include/linux/pci.h
> >> index aab57b4..5f6f8fa 100644
> >> --- a/include/linux/pci.h
> >> +++ b/include/linux/pci.h
> >> @@ -1129,6 +1129,19 @@ resource_size_t pcibios_window_alignment(struct pci_bus *bus,
> >>   
> >>   int pci_set_vga_state(struct pci_dev *pdev, bool decode,
> >>   		      unsigned int command_bits, u32 flags);
> >> +/* helper functions for operation of device flag */
> >> +static inline void pci_set_dev_assigned(struct pci_dev *pdev)
> >> +{
> >> +	pdev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
> >> +}
> >> +static inline void pci_set_dev_deassigned(struct pci_dev *pdev)
> >> +{
> >> +	pdev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> >> +}
> > I think pci_clear_dev_assigned() would make more sense, we're not
> > setting a flag named DEASSIGNED.
>    Though it is a flag operation now, may not later, we define it 
> because we want to hide the internal operation.
>    'set' to 'deassigned'  status is enough. So I would like keep it.

I disagree, the opposite of a 'set' is a 'clear', or at least an
'unset'.  Using bit-ops-like terminology doesn't lock us into an
implementation.  As written, this could just as easily be setting two
different variables.

> >
> >> +static inline bool pci_is_dev_assigned(struct pci_dev *pdev)
> >> +{
> >> +	return pdev->dev_flags & PCI_DEV_FLAGS_ASSIGNED ? true : false;
> >> +}
> > The ternary operation isn't necessary.  Thanks,
>    Yep,
> 
>    return pdev->dev_flags & PCI_DEV_FLAGS_ASSIGNED
> 
>    is enough.
> 
>    Thanks,
>    Ethan
> >
> > Alex
> >
> >>   /* kmem_cache style wrapper around pci_alloc_consistent() */
> >>   
> >>   #include <linux/pci-dma.h>
> >
> >
> 



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