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

[ethan zhao <ethan.zhao@xxxxxxxxxx>]

On 2014/7/29 10:31, Alex Williamson wrote:
> 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@xxxxxxxxxx>
> > > > ---
> > > >    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.
 So there are two pairs of opposite:

 set assigned ---> unset assigned
 set assigned ---> set deassigned

 Here you prefer the 'verb' set /unset, and I prefer the 'adj.' 
assigned / deassigned.
 Do they really have different meaning or make confusion ? I don't 
think so.
 Thanks,
 Ethan

> > > > +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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