linux-kernel - Re: [PATCH v2 2/2] misc: Add iop driver for Sunplus SP7021

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Message-ID: <CAK8P3a2AgO2R-yQsT6nkiVU0J6pXa-bMnckrShey2EUZjAq3Uw@mail.gmail.com>
Date:   Mon, 6 Dec 2021 09:04:14 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Tony Huang 黃懷厚 <tony.huang@...plus.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Tony Huang <tonyhuang.sunplus@...il.com>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        gregkh <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        Wells Lu 呂芳騰 <wells.lu@...plus.com>
Subject: Re: [PATCH v2 2/2] misc: Add iop driver for Sunplus SP7021

On Mon, Dec 6, 2021 at 4:42 AM Tony Huang 黃懷厚 <tony.huang@...plus.com> wrote:
> > Subject: Re: [PATCH v2 2/2] misc: Add iop driver for Sunplus SP7021
> > On Fri, Dec 3, 2021 at 4:48 AM Tony Huang <tonyhuang.sunplus@...il.com> wrote:
> > > +
> > > +static const struct file_operations sp_iop_fops = {
> > > +       .owner                  = THIS_MODULE,
> > > +       .open                   = sp_iop_open,
> > > +       .read                   = sp_iop_read,
> > > +       .write                  = sp_iop_write,
> > > +       .release                = sp_iop_release,
> > > +};
> >
> > This does nothing because all the callbacks are empty. You removed the
> > inappropriate user space interfaces as I asked you to, but if there is no way for
> > either kernel or user space to interact with the hardware, I don't see a point in
> > merging the driver until you add a new interface that is usable.
> >
>
> I will modify sp_iop_read() to monitor IOP mailbox data.

Why is this a useful interface to have? If this is only for debugging,
a tracepoint
may be more useful than a full character device.

> > Something looks wrong here, maybe reread the documentation for runtime
> > power management to find a way of putting the device into low-power mode
> > when it is unused.
> >
>
> When the poweroff command is executed, the run sp_iop_platform_driver_poweroff(void)
> function will enter the standby mode. The power off will be executed.
> In the system, IOP can continue to work when other modules in the system enter
> standby / power down modes to monitor whether the system wakes up through RTC.

Ok, in that case you can probably just remove the empty callback functions.

         Arnd