Re: [PATCH] xen/arm: smmuv3: remove unused function

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

On 12/12/22 11:24, Rahul Singh wrote:
> Hi Julien,
> 
>> On 12 Dec 2022, at 4:07 pm, Julien Grall <julien@xxxxxxx> wrote:
>>
>> Hi Stewart,
>>
>> On 12/12/2022 16:00, Stewart Hildebrand wrote:
>>> When building with clang 12 and CONFIG_ARM_SMMU_V3=y, we observe the
>>> following build error:
>>> drivers/passthrough/arm/smmu-v3.c:1408:20: error: unused function 
>>> 'arm_smmu_disable_pasid' [-Werror,-Wunused-function]
>>> static inline void arm_smmu_disable_pasid(struct arm_smmu_master *master) { 
>>> }
>>>                    ^
>>> Remove the function.
>>> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
>>> ---
>>> There is also a definition of arm_smmu_disable_pasid() just above,
>>> guarded by #ifdef CONFIG_PCI_ATS. Should this one be removed too? It
>>> might be nice to keep this definition for ease of backporting patches
>>> from Linux, but if we ever plan on supporting PCI_ATS in Xen this may
>>> need to be re-visited.
>>
>> Given the function is not called at all, I think this is a bit odd to remove 
>> the stub but leave the implementation when CONFIG_PCI_ATS is defined.
>>
>> Rahul, do you plan to use it in the PCI passthrough code? If yes, then I 
>> would consider to use __maybe_unused.
> 
> No, this function will not be used in PCI passthrough code, but when we 
> merged the SMMUv3 code from Linux at that time we
> decided to have this code and gate with CONFIG_PCI_ATS so that in the future 
> if someone wants to implement the PASID feature
> will use these functions.
> 
> I also agree with Julien we would consider using __maybe_unused.

OK, I will send a v2 with the __maybe_unused attribute (in both locations), in 
case PASID is to be implemented in the future.