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From:   Leonard Crestez <leonard.crestez@nxp.com>
To:     Marco Felsch <m.felsch@pengutronix.de>,
        Anson Huang <anson.huang@nxp.com>
CC:     Aisheng Dong <aisheng.dong@nxp.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
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        "festevam@gmail.com" <festevam@gmail.com>,
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        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH] firmware: imx: Skip return value check for some special
 SCU firmware APIs
Thread-Topic: [PATCH] firmware: imx: Skip return value check for some special
 SCU firmware APIs
Thread-Index: AQHVc4lSn4nBMGf230anvZh0PllY6g==
Date:   Fri, 27 Sep 2019 11:22:22 +0000
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On 27.09.2019 12:06, Marco Felsch wrote:=0A=
> Hi Anson, Leonard,=0A=
> =0A=
> On 19-09-27 01:20, Anson Huang wrote:=0A=
>> Hi, Leonard=0A=
>>=0A=
>>> On 2019-09-26 1:06 PM, Marco Felsch wrote:=0A=
>>>> On 19-09-26 08:03, Anson Huang wrote:=0A=
>>>>>> On 19-09-25 18:07, Anson Huang wrote:=0A=
>>>>>>> The SCU firmware does NOT always have return value stored in=0A=
>>>>>>> message header's function element even the API has response data,=
=0A=
>>>>>>> those special APIs are defined as void function in SCU firmware, so=
=0A=
>>>>>>> they should be treated as return success always.=0A=
>>>>>>>=0A=
>>>>>>> +static const struct imx_sc_rpc_msg whitelist[] =3D {=0A=
>>>>>>> +	{ .svc =3D IMX_SC_RPC_SVC_MISC, .func =3D=0A=
>>>>>> IMX_SC_MISC_FUNC_UNIQUE_ID },=0A=
>>>>>>> +	{ .svc =3D IMX_SC_RPC_SVC_MISC, .func =3D=0A=
>>>>>>> +IMX_SC_MISC_FUNC_GET_BUTTON_STATUS }, };=0A=
>>>>>>=0A=
>>>>>> Is this going to be extended in the near future? I see some upcoming=
=0A=
>>>>>> problems here if someone uses a different scu-fw<->kernel=0A=
>>>>>> combination as nxp would suggest.=0A=
>>>>>=0A=
>>>>> Could be, but I checked the current APIs, ONLY these 2 will be used=
=0A=
>>>>> in Linux kernel, so I ONLY add these 2 APIs for now.=0A=
>>>>=0A=
>>>> Okay.=0A=
>>>>=0A=
>>>>> However, after rethink, maybe we should add another imx_sc_rpc API=0A=
>>>>> for those special APIs? To avoid checking it for all the APIs called =
which=0A=
>>> may impact some performance.=0A=
>>>>> Still under discussion, if you have better idea, please advise, thank=
s!=0A=
>>>=0A=
>>> My suggestion is to refactor the code and add a new API for the this "n=
o=0A=
>>> error value" convention. Internally they can call a common function wit=
h=0A=
>>> flags.=0A=
>>=0A=
>>>> Adding a special api shouldn't be the right fix. Imagine if someone=0A=
>>>> (not a nxp-developer) wants to add a new driver. How could he be=0A=
>>>> expected to know which api he should use. The better abbroach would be=
=0A=
>>>> to fix the scu-fw instead of adding quirks..=0A=
>>=0A=
>> Yes, fixing SCU FW is the best solution, but we have talked to SCU FW ow=
ner, the SCU=0A=
>> FW released has been finalized, so the API implementation can NOT be cha=
nged, but=0A=
>> they will pay attention to this issue for new added APIs later. That mea=
ns the number=0A=
>> of APIs having this issue a very limited.=0A=
> =0A=
> This means those APIs which already have this bug will not be fixed?=0A=
> IMHO this sounds a bit weird since this is a changeable peace of code ;)=
=0A=
=0A=
It's not a bug, it's a documented feature ;)=0A=
=0A=
>>> Right now developers who want to make SCFW calls in upstream need to=0A=
>>> define the message struct in their driver based on protocol documentati=
on.=0A=
>>> This includes:=0A=
>>>=0A=
>>> * Binary layout of the message (a packed struct)=0A=
>>> * If the message has a response (already a bool flag)=0A=
>>> * If an error code is returned (this patch adds support for it)=0A=
> =0A=
> Why should I specify if a error code is returned?=0A=
=0A=
Because you're already defining the message struct and you're already =0A=
specifying if a response is required.=0A=
=0A=
The assumption is that anyone adding a SCFW call to a driver is already =0A=
looking at SCFW documentation which describes the binary message format.=0A=
=0A=
--=0A=
Regards,=0A=
Leonard=0A=