Re: [PATCH V2 4/4] PCI: consolidate return value check for pci_find_(ext_)capability

[Wei Yang <weiyang@linux.vnet.ibm.com>]

On Tue, Jul 14, 2015 at 05:00:21PM -0500, Bjorn Helgaas wrote:
>On Tue, Jun 30, 2015 at 09:16:44AM +0800, Wei Yang wrote:
>> The return value of the pci_find_(ext_)capability is the position of this
>> Cap.  After previous two patches clean up, the position returned is an
>> unsigned value. Only 0 indicates the Cap is not presented.
>> 
>> This patch consolidates the form of check from (pos <= 0)to (!pos).
>> 
>> Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
>
>Applied to pci/misc with changelog as below.
>
>It seems pretty clear to me that pci_find_capability() returns either 0 or
>a u8 value.  pci_find_ext_capability() does return an int.  It looks to me
>like it can never be negative, but if you wanted it to be even more clear,
>you could easily change just pci_find_next_ext_capability() to use a u16
>for "pos".  That would be very simple and wouldn't change any interfaces.

pci_find_capability() will return either 0 or a u8 value, while in the code
the return value is an "int" type. So for the first sight, it may not that
immediate. The same as pci_find_ext_capability().

This is the reason for patch 2/3. The purpose is to make the return type
reflect the value it will return.

Patch 3 does exactly what you said, use a u16 for "pos" in
pci_find_next_ext_capability().

>
>commit d5fa86074987b1b5fcbfba8c9315e75ff7262f71
>Author: Wei Yang <weiyang@linux.vnet.ibm.com>
>Date:   Tue Jun 30 09:16:44 2015 +0800
>
>    PCI: Simplify pci_find_(ext_)capability() return value checks
>    
>    The return value of the pci_find_(ext_)capability() is either zero or the
>    position of a capability.  It is never negative.
>    
>    This patch consolidates the form of check from (pos <= 0) to (!pos).
>    
>    Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
>    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

-- 
Richard Yang
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