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

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Date:	Tue, 29 Jul 2014 10:43:33 +0800
From:	ethan zhao <ethan.zhao@...cle.com>
To:	Alex Williamson <alex.williamson@...hat.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 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@...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.
  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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