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

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Date:	Tue, 29 Jul 2014 11:47:42 +0800
From:	Ethan Zhao <ethan.kernel@...il.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	ethan zhao <ethan.zhao@...cle.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci <linux-pci@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"<gleb@...nel.org>" <gleb@...nel.org>,
	"<pbonzini@...hat.com>" <pbonzini@...hat.com>,
	"<kvm@...r.kernel.org>" <kvm@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"<boris.ostrovsky@...cle.com>" <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	xen-devel@...ts.xenproject.org,
	"<alexander.h.duyck@...el.com>" <alexander.h.duyck@...el.com>
Subject: Re: [PATCH 1/4] PCI: introduce helper functions for device flag operation

Both of you and Alex W prefer the 'Verb' , Ok,  I accept the suggestion.

Thanks,
Ethan


On Tue, Jul 29, 2014 at 11:37 AM, Alexander Duyck
<alexander.duyck@...il.com> wrote:
> On 07/28/2014 07:43 PM, ethan zhao wrote:
>>
>> 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
>>
>
> I agree with Alex W.  If you are going to use the "set" name you should
> probably use "clear" for the operation that undoes it.  Using the term
> set implies that it is setting a bit and we currently don't have a
> deassigned/unassigned bit.
>
> If that doesn't work perhaps you could use something like
> get/put_assigned_device or acquire/release_assigned_device.  You just
> need to describe what it is you are doing.  You could even consider
> adding some tests to return an error if you attempt to assign a device
> that is already assigned.
>
> Thanks,
>
> Alex D
>
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