Re: [PATCH net-next 3/3] net: ethernet: ti: cpsw_ale: Remove unused accessor functions

[Roger Quadros <rogerq@kernel.org>]

On 12/09/2024 11:59, Simon Horman wrote:
> On Thu, Sep 12, 2024 at 10:07:27AM +0300, Roger Quadros wrote:
>> Hi Simon,
>>
>> On 10/09/2024 10:17, Simon Horman wrote:
>>> W=1 builds flag that some accessor functions for ALE fields are unused.
>>>
>>> Address this by splitting up the macros used to define these
>>> accessors to allow only those that are used to be declared.
>>>
>>> The warnings are verbose, but for example, the mcast_state case is
>>> flagged by clang-18 as:
>>>
>>> .../cpsw_ale.c:220:1: warning: unused function 'cpsw_ale_get_mcast_state' [-Wunused-function]
>>>   220 | DEFINE_ALE_FIELD(mcast_state,           62,     2)
>>>       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> .../cpsw_ale.c:145:19: note: expanded from macro 'DEFINE_ALE_FIELD'
>>>   145 | static inline int cpsw_ale_get_##name(u32 *ale_entry)                   \
>>>       |                   ^~~~~~~~~~~~~~~~~~~
>>> <scratch space>:196:1: note: expanded from here
>>>   196 | cpsw_ale_get_mcast_state
>>>       | ^~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Compile tested only.
>>> No functional change intended.
>>>
>>> Signed-off-by: Simon Horman <horms@kernel.org>
>>> ---
>>>  drivers/net/ethernet/ti/cpsw_ale.c | 30 +++++++++++++++++++++---------
>>>  1 file changed, 21 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/ti/cpsw_ale.c b/drivers/net/ethernet/ti/cpsw_ale.c
>>> index 64bf22cd860c..d37b4ddd6787 100644
>>> --- a/drivers/net/ethernet/ti/cpsw_ale.c
>>> +++ b/drivers/net/ethernet/ti/cpsw_ale.c
>>> @@ -141,27 +141,39 @@ static inline void cpsw_ale_set_field(u32 *ale_entry, u32 start, u32 bits,
>>>  	ale_entry[idx] |=  (value << start);
>>>  }
>>>  
>>> -#define DEFINE_ALE_FIELD(name, start, bits)				\
>>> +#define DEFINE_ALE_FIELD_GET(name, start, bits)				\
>>>  static inline int cpsw_ale_get_##name(u32 *ale_entry)			\
>>>  {									\
>>>  	return cpsw_ale_get_field(ale_entry, start, bits);		\
>>> -}									\
>>> +}
>>> +
>>> +#define DEFINE_ALE_FIELD_SET(name, start, bits)				\
>>>  static inline void cpsw_ale_set_##name(u32 *ale_entry, u32 value)	\
>>>  {									\
>>>  	cpsw_ale_set_field(ale_entry, start, bits, value);		\
>>>  }
>>>  
>>> -#define DEFINE_ALE_FIELD1(name, start)					\
>>> +#define DEFINE_ALE_FIELD(name, start, bits)				\
>>> +DEFINE_ALE_FIELD_GET(name, start, bits)					\
>>> +DEFINE_ALE_FIELD_SET(name, start, bits)
>>> +
>>> +#define DEFINE_ALE_FIELD1_GET(name, start)				\
>>>  static inline int cpsw_ale_get_##name(u32 *ale_entry, u32 bits)		\
>>>  {									\
>>>  	return cpsw_ale_get_field(ale_entry, start, bits);		\
>>> -}									\
>>> +}
>>> +
>>> +#define DEFINE_ALE_FIELD1_SET(name, start)				\
>>>  static inline void cpsw_ale_set_##name(u32 *ale_entry, u32 value,	\
>>>  		u32 bits)						\
>>>  {									\
>>>  	cpsw_ale_set_field(ale_entry, start, bits, value);		\
>>>  }
>>>  
>>> +#define DEFINE_ALE_FIELD1(name, start)					\
>>> +DEFINE_ALE_FIELD1_GET(name, start)					\
>>> +DEFINE_ALE_FIELD1_SET(name, start)
>>> +
>>>  enum {
>>>  	ALE_ENT_VID_MEMBER_LIST = 0,
>>>  	ALE_ENT_VID_UNREG_MCAST_MSK,
>>> @@ -217,14 +229,14 @@ static const struct ale_entry_fld vlan_entry_k3_cpswxg[] = {
>>>  
>>>  DEFINE_ALE_FIELD(entry_type,		60,	2)
>>>  DEFINE_ALE_FIELD(vlan_id,		48,	12)
>>> -DEFINE_ALE_FIELD(mcast_state,		62,	2)
>>> +DEFINE_ALE_FIELD_SET(mcast_state,	62,	2)
>>
>> I don't understand why we need separate macros for GET and SET.
>> The original intent was to use one macro for both.
>>
>> Otherwise we will have to add DEFINE_ALE_FIELD/1_SET to all the fields.
> 
> Hi Roger,
> 
> Sorry for not being clearer.
> 
> My intent was to avoid declaring functions that are never used.
> Perhaps it is best explained by some examples.
> 
> In the case of mcast_state, the compiler flags that the get accessor is
> never used. The intent is of this patch addresses that by declaring the set
> accessor for mcast_state. Likewise for other similar cases.
> 
> OTOH, in the case of, f.e. vlan_id, the set and get accessor functions are
> both used, and DEFINE_ALE_FIELD continues to be used to define them both.
> DEFINE_ALE_FIELD is implemented as the combination of _SET and _GET.
> 

Thanks for the explanation Simon. I understand now.

Would using __maybe_unused__ be preferable to get rid of the warnings?
That way we don't need to care if both set/get helpers are used or not
and don't have to touch the below code ever again except to add new fields.

>>
>>>  DEFINE_ALE_FIELD1(port_mask,		66)
>>>  DEFINE_ALE_FIELD(super,			65,	1)
>>>  DEFINE_ALE_FIELD(ucast_type,		62,     2)
>>> -DEFINE_ALE_FIELD1(port_num,		66)
>>> -DEFINE_ALE_FIELD(blocked,		65,     1)
>>> -DEFINE_ALE_FIELD(secure,		64,     1)
>>> -DEFINE_ALE_FIELD(mcast,			40,	1)
>>> +DEFINE_ALE_FIELD1_SET(port_num,		66)
>>> +DEFINE_ALE_FIELD_SET(blocked,		65,     1)
>>> +DEFINE_ALE_FIELD_SET(secure,		64,     1)
>>> +DEFINE_ALE_FIELD_GET(mcast,		40,	1)
>>>  
>>>  #define NU_VLAN_UNREG_MCAST_IDX	1
>>>  
>>>
>>

-- 
cheers,
-roger