Dear Arnd:

-----Original Message-----
From: Arnd Bergmann <arnd@arndb.de>
Sent: Monday, December 6, 2021 4:04 PM
To: Tony Huang 黃懷厚 <redacted>
Cc: Arnd Bergmann <arnd@arndb.de>; Tony Huang
[off-list ref]; Derek Kiernan [off-list ref];
Dragan Cvetic [off-list ref]; gregkh
[off-list ref]; Linux Kernel Mailing List
[off-list ref]; Rob Herring [off-list ref]; DTML
[off-list ref]; Wells Lu 呂芳騰 [off-list ref]
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
[off-list ref] wrote:

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Subject: Re: [PATCH v2 2/2] misc: Add iop driver for Sunplus SP7021
On Fri, Dec 3, 2021 at 4:48 AM Tony Huang

[off-list ref] wrote:

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+
+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.

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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.

Yes, it is for debugging.

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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