linux-kernel - Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier) support

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Date:   Thu, 27 Jun 2019 09:43:34 +0300
From:   Daniel Baluta <daniel.baluta@...il.com>
To:     Anson Huang <anson.huang@....com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Aisheng Dong <aisheng.dong@....com>,
        Abel Vesa <abel.vesa@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        Daniel Baluta <daniel.baluta@....com>
Subject: Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier) support

On Thu, Jun 27, 2019 at 3:48 AM Anson Huang <anson.huang@....com> wrote:
>
> Hi, Daniel
>
> > -----Original Message-----
> > From: Daniel Baluta <daniel.baluta@...il.com>
> > Sent: Wednesday, June 26, 2019 8:42 PM
> > To: Anson Huang <anson.huang@....com>
> > Cc: Shawn Guo <shawnguo@...nel.org>; Sascha Hauer
> > <s.hauer@...gutronix.de>; Pengutronix Kernel Team
> > <kernel@...gutronix.de>; Fabio Estevam <festevam@...il.com>; Aisheng
> > Dong <aisheng.dong@....com>; Abel Vesa <abel.vesa@....com>; linux-
> > arm-kernel <linux-arm-kernel@...ts.infradead.org>; Linux Kernel Mailing List
> > <linux-kernel@...r.kernel.org>; dl-linux-imx <linux-imx@....com>; Daniel
> > Baluta <daniel.baluta@....com>
> > Subject: Re: [PATCH] soc: imx-scu: Add SoC UID(unique identifier) support
> >
> > On Wed, Jun 26, 2019 at 10:06 AM <Anson.Huang@....com> wrote:
> > >
> > > From: Anson Huang <Anson.Huang@....com>
> > >
> > > Add i.MX SCU SoC's UID(unique identifier) support, user can read it
> > > from sysfs:
> > >
> > > root@...8qxpmek:~# cat /sys/devices/soc0/soc_uid
> > > 7B64280B57AC1898
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > > ---
> > >  drivers/soc/imx/soc-imx-scu.c | 35
> > > +++++++++++++++++++++++++++++++++++
> > >  1 file changed, 35 insertions(+)
> > >
> > > diff --git a/drivers/soc/imx/soc-imx-scu.c
> > > b/drivers/soc/imx/soc-imx-scu.c index 676f612..8d322a1 100644
> > > --- a/drivers/soc/imx/soc-imx-scu.c
> > > +++ b/drivers/soc/imx/soc-imx-scu.c
> > > @@ -27,6 +27,36 @@ struct imx_sc_msg_misc_get_soc_id {
> > >         } data;
> > >  } __packed;
> > >
> > > +struct imx_sc_msg_misc_get_soc_uid {
> > > +       struct imx_sc_rpc_msg hdr;
> > > +       u32 uid_low;
> > > +       u32 uid_high;
> > > +} __packed;
> > > +
> > > +static ssize_t soc_uid_show(struct device *dev,
> > > +                           struct device_attribute *attr, char *buf)
> > > +{
> > > +       struct imx_sc_msg_misc_get_soc_uid msg;
> > > +       struct imx_sc_rpc_msg *hdr = &msg.hdr;
> > > +       u64 soc_uid;
> > > +
> > > +       hdr->ver = IMX_SC_RPC_VERSION;
> > > +       hdr->svc = IMX_SC_RPC_SVC_MISC;
> > > +       hdr->func = IMX_SC_MISC_FUNC_UNIQUE_ID;
> > > +       hdr->size = 1;
> > > +
> > > +       /* the return value of SCU FW is in correct, skip return value
> > > + check */
> >
> > Why do you mean by "in correct"?
>
> I made a mistake, it should be "incorrect", the existing SCFW of this API returns
> an error value even this API is successfully called, to make it work with current
> SCFW, I have to skip the return value check for this API for now. Will send V2 patch
> to fix this typo.

Thanks Anson! It makes sense now. It is a little bit sad though because we won't
know when there is a "real" error :).

Lets update the comment to be more specific:

/* SCFW FW API always returns an error even the function is
successfully executed, so skip returned value */


> > > +       imx_scu_call_rpc(soc_ipc_handle, &msg, true);
> > > +
> > > +       soc_uid = msg.uid_high;
> > > +       soc_uid <<= 32;
> > > +       soc_uid |= msg.uid_low;
> > > +
> > > +       return sprintf(buf, "%016llX\n", soc_uid);
> >
> > snprintf?
>
> The snprintf is to avoid buffer overflow, which in this case, I don't know the size
> of "buf", and the value(u64) to be printed is with fixed length of 64, so I think
> sprint is just OK.

Ok.