linux-kernel - Re: [PATCH v4 4/4] firmware: arm_scmi: Add qcom hvc/shmem transport support

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Message-ID: <69b8ded0-7648-80bd-c41b-c591b0f861ef@quicinc.com>
Date:   Thu, 5 Oct 2023 15:33:14 -0700
From:   Nikunj Kela <quic_nkela@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Sudeep Holla <sudeep.holla@....com>
CC:     <cristian.marussi@....com>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <andersson@...nel.org>, <konrad.dybcio@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] firmware: arm_scmi: Add qcom hvc/shmem transport
 support


On 10/5/2023 3:20 PM, Bjorn Andersson wrote:
> On Wed, Oct 04, 2023 at 05:06:30PM +0100, Sudeep Holla wrote:
>> On Tue, Oct 03, 2023 at 09:16:27AM -0700, Nikunj Kela wrote:
>>> On 10/3/2023 4:19 AM, Sudeep Holla wrote:
>>>> On Mon, Sep 11, 2023 at 12:43:59PM -0700, Nikunj Kela wrote:
>>>>> diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c
> [..]
>>>>> @@ -63,6 +66,8 @@ struct scmi_smc {
>>>>>    	u32 func_id;
>>>>>    	u32 param_page;
>>>>>    	u32 param_offset;
>>>>> +	u64 cap_id;
>>>> Can it be unsigned long instead so that it just works for both 32 and 64 bit.
>>> My first version of this patch was ulong but Bjorn suggested to make this
>>> structure size fixed i.e. architecture independent. Hence changed it to u64.
>>> If you are ok with ulong, I can change it back to ulong.
>>>
>> SMCCC pre-v1.2 used the common structure in that way. I don't see any issue
>> with that. I haven't followed Bjorn suggestions/comments though.
>>
> My request was that funcId and capId is an ABI between the firmware and
> the OS, so I'd like for that to use well defined, fixed sized, data
> types - if nothing else just for documentation purpose.
>
> These values will be truncated when passed to arm_smccc_1_1_invoke()
> anyways, so I don't have any opinion against using unsigned long here...
>
>
> PS. I understand why func_id is u32, but why are param_page and
> param_offset u32?

That was done to keep it uniform across smc32/smc64 conventions.

>
> Regards,
> Bjorn