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

[Arnd Bergmann <arnd@arndb.de>]

On Mon, Dec 6, 2021 at 4:42 AM Tony Huang 黃懷厚 <tony.huang@sunplus.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@gmail.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