linux-kernel - Re: [PATCH v3] PM / core: conditionally skip system pm in device/driver model

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Message-ID: <2024022901-getaway-bacon-b805@gregkh>
Date: Thu, 29 Feb 2024 21:34:26 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Guan-Yu Lin <guanyulin@...gle.com>
Cc: Florian Fainelli <f.fainelli@...il.com>, rafael@...nel.org,
	pavel@....cz, len.brown@...el.com,
	andriy.shevchenko@...ux.intel.com, rdunlap@...radead.org,
	james@...iv.tech, broonie@...nel.org, james.clark@....com,
	masahiroy@...nel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v3] PM / core: conditionally skip system pm in
 device/driver model

On Thu, Feb 29, 2024 at 05:08:00PM +0800, Guan-Yu Lin wrote:
> We want to introduce a mechanism that allows the Linux kernel to make
> power transitions for the peripheral based on whether the other
> operating system kernel is actively using it. To achieve this, we
> propose this patch that adds a sysfs attribute, providing the Linux
> kernel with the necessary information.

Don't create random user/kernel apis in sysfs for no good reason just
because it is "easy" :(

If the "other operating system is actively using it" isn't able to be
detected by Linux, then Linux shouldn't be able to change the PM state,
so this sounds like you need to fix your Linux driver to properly know
this information, just like any other device type (think about a sound
device that needs to know if it is being used or not, nothing different
here.)

So please post your Linux driver and we can see what needs to be done
there to get this to work properly, odds are you are just missing
something.  Have a pointer to the code anywhere?

Also, as you know, we can NOT add interfaces to the kernel without any
real user, so without a driver for your hardware, none of this is able
to go anywhere at all, sorry.

thanks,

greg k-h