Re: [PATCH] net: Abstract features usage.

[Mahesh Bandewar <maheshb@google.com>]

On Tue, May 24, 2011 at 2:29 PM, Stephen Hemminger
<shemminger@vyatta.com> wrote:
> On Tue, 24 May 2011 11:52:42 -0700
> Mahesh Bandewar <maheshb@google.com> wrote:
>
>> Define macros to set/clear/test bits for feature set usage. This will eliminate
>> the direct use of these fields and enable future ease in managing these fields.
>>
>> Signed-off-by: Mahesh Bandewar <maheshb@google.com>
>> ---
>>  include/linux/netdev_features.h |  137 +++++++++++++++++++++++++++++++++++++++
>>  include/linux/netdevice.h       |   35 ++---------
>>  2 files changed, 142 insertions(+), 30 deletions(-)
>>  create mode 100644 include/linux/netdev_features.h
>>
>> diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
>> new file mode 100644
>> index 0000000..97bf8c4
>> --- /dev/null
>> +++ b/include/linux/netdev_features.h
>> @@ -0,0 +1,137 @@
>> +#ifndef      _NETDEV_FEATURES_H
>> +#define      _NETDEV_FEATURES_H
>> +
>> +/* Forward declarations */
>> +struct net_device;
>> +
>> +typedef      unsigned long *nd_feature_t
>
> typedef'ing a pointer is strongly discouraged by kernel coding style.
> You need to use another way such as open coding it.
>
The idea here is to have a typedef that we can use to avoid future
changes all over the code if we decide to change the way feature bits
are stored. So if this is bitmap it will be defined as "unsigned long
*" and if it were to be u64 then it's typedef-ed as "u64". So in one
case it's a pointer and in other case it's not! Now how do we handle
both these cases?

Thanks,
--mahesh..

> --
>