Re: [PATCH] firmware: imx: Skip return value check for some special SCU firmware APIs

[Leonard Crestez]

On 27.09.2019 12:06, Marco Felsch wrote:
> Hi Anson, Leonard,
> 
> On 19-09-27 01:20, Anson Huang wrote:
>> Hi, Leonard
>>
>>> On 2019-09-26 1:06 PM, Marco Felsch wrote:
>>>> On 19-09-26 08:03, Anson Huang wrote:
>>>>>> On 19-09-25 18:07, Anson Huang wrote:
>>>>>>> The SCU firmware does NOT always have return value stored in
>>>>>>> message header's function element even the API has response data,
>>>>>>> those special APIs are defined as void function in SCU firmware, so
>>>>>>> they should be treated as return success always.
>>>>>>>
>>>>>>> +static const struct imx_sc_rpc_msg whitelist[] = {
>>>>>>> +	{ .svc = IMX_SC_RPC_SVC_MISC, .func =
>>>>>> IMX_SC_MISC_FUNC_UNIQUE_ID },
>>>>>>> +	{ .svc = IMX_SC_RPC_SVC_MISC, .func =
>>>>>>> +IMX_SC_MISC_FUNC_GET_BUTTON_STATUS }, };
>>>>>>
>>>>>> Is this going to be extended in the near future? I see some upcoming
>>>>>> problems here if someone uses a different scu-fw<->kernel
>>>>>> combination as nxp would suggest.
>>>>>
>>>>> Could be, but I checked the current APIs, ONLY these 2 will be used
>>>>> in Linux kernel, so I ONLY add these 2 APIs for now.
>>>>
>>>> Okay.
>>>>
>>>>> However, after rethink, maybe we should add another imx_sc_rpc API
>>>>> for those special APIs? To avoid checking it for all the APIs called which
>>> may impact some performance.
>>>>> Still under discussion, if you have better idea, please advise, thanks!
>>>
>>> My suggestion is to refactor the code and add a new API for the this "no
>>> error value" convention. Internally they can call a common function with
>>> flags.
>>
>>>> Adding a special api shouldn't be the right fix. Imagine if someone
>>>> (not a nxp-developer) wants to add a new driver. How could he be
>>>> expected to know which api he should use. The better abbroach would be
>>>> to fix the scu-fw instead of adding quirks..
>>
>> Yes, fixing SCU FW is the best solution, but we have talked to SCU FW owner, the SCU
>> FW released has been finalized, so the API implementation can NOT be changed, but
>> they will pay attention to this issue for new added APIs later. That means the number
>> of APIs having this issue a very limited.
> 
> This means those APIs which already have this bug will not be fixed?
> IMHO this sounds a bit weird since this is a changeable peace of code ;)

It's not a bug, it's a documented feature ;)

>>> Right now developers who want to make SCFW calls in upstream need to
>>> define the message struct in their driver based on protocol documentation.
>>> This includes:
>>>
>>> * Binary layout of the message (a packed struct)
>>> * If the message has a response (already a bool flag)
>>> * If an error code is returned (this patch adds support for it)
> 
> Why should I specify if a error code is returned?

Because you're already defining the message struct and you're already 
specifying if a response is required.

The assumption is that anyone adding a SCFW call to a driver is already 
looking at SCFW documentation which describes the binary message format.

--
Regards,
Leonard