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

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Message-ID: <20231006072650.ubgcnbda7daynofa@bogus>
Date:   Fri, 6 Oct 2023 08:26:50 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Nikunj Kela <quic_nkela@...cinc.com>, 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 Thu, Oct 05, 2023 at 03:20:16PM -0700, 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?
> 

Good point. Sorry I somehow missed your original comment, my bad.
Yes, it is good to be consistent. Sorry if I added any confusion by
missing o read your comment and understanding it before I responded.

--
Regards,
Sudeep