From: Andrew Lunn <and...@lunn.ch>
Date: Tue, 30 May 2017 17:01:44 +0200
> On Tue, May 30, 2017 at 10:21:25AM -0400, Vivien Didelot wrote:
>> Hide the implementation of dsa_uses_tagged_protocol in dsa.c since this
>> helper will be extended to access the opaque dsa_device_ops structure.
>>
>> At the same time, fix the checkpatch comparison check:
>>
>> CHECK: Comparison to NULL could be written "dst->rcv"
>> #41: FILE: net/dsa/dsa.c:32:
>> + return dst->rcv != NULL;
>>
>> Signed-off-by: Vivien Didelot <vivien.dide...@savoirfairelinux.com>
>> ---
>> include/net/dsa.h | 5 +----
>> net/dsa/dsa.c | 5 +++++
>> 2 files changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/net/dsa.h b/include/net/dsa.h
>> index c0e567c0c824..cb5d668b265d 100644
>> --- a/include/net/dsa.h
>> +++ b/include/net/dsa.h
>> @@ -464,10 +464,7 @@ struct mii_bus *dsa_host_dev_to_mii_bus(struct device
>> *dev);
>>
>> struct net_device *dsa_dev_to_net_device(struct device *dev);
>>
>> -static inline bool dsa_uses_tagged_protocol(struct dsa_switch_tree *dst)
>> -{
>> - return dst->rcv != NULL;
>> -}
>> +bool dsa_uses_tagged_protocol(struct dsa_switch_tree *dst);
>>
>> static inline bool netdev_uses_dsa(struct net_device *dev)
>> {
>> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
>> index 3288a80d4d6c..7a8a0358299b 100644
>> --- a/net/dsa/dsa.c
>> +++ b/net/dsa/dsa.c
>> @@ -27,6 +27,11 @@
>>
>> #include "dsa_priv.h"
>>
>> +bool dsa_uses_tagged_protocol(struct dsa_switch_tree *dst)
>> +{
>> + return !!dst->rcv;
>> +}
>> +
>
> Hi Vivien
>
> You need to be careful here. This is in the hot path. Every frame
> received uses this code. And think about a distro kernel, which might
> have DSA enabled by default, yet is unlikely to have any switches. You
> are adding a function call which can be called millions of times per
> second....
Yeah, we really can't make this change.
This isn't glibc where we're trying to hide the implementation of "FILE *"
behind accessor functions that caller can't see. We inline things when
performance dictates, and it does here.
