linux-kernel - Re: [PATCH v3 11/13] hwmon: (xgene-hwmon) Simplify PCC shared memory region handling

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Message-ID: <20250411-able-rattlesnake-of-calibration-fcdcd8@sudeepholla>
Date: Fri, 11 Apr 2025 16:07:44 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jassi Brar <jassisinghbrar@...il.com>,
	Huisong Li <lihuisong@...wei.com>,
	Adam Young <admiyo@...amperecomputing.com>,
	Robbie King <robbiek@...ghtlabs.com>,
	Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v3 11/13] hwmon: (xgene-hwmon) Simplify PCC shared memory
 region handling

On Fri, Apr 11, 2025 at 07:15:22AM -0700, Guenter Roeck wrote:
> On Thu, Mar 13, 2025 at 03:28:57PM +0000, Sudeep Holla wrote:
> > The PCC driver now handles mapping and unmapping of shared memory
> > areas as part of pcc_mbox_{request,free}_channel(). Without these before,
> > this xgene hwmon driver did handling of those mappings like several
> > other PCC mailbox client drivers.
> > 
> > There were redundant operations, leading to unnecessary code. Maintaining
> > the consistency across these driver was harder due to scattered handling
> > of shmem.
> > 
> > Just use the mapped shmem and remove all redundant operations from this
> > driver.
> > 
> > Cc: Jean Delvare <jdelvare@...e.com>
> > Cc: Guenter Roeck <linux@...ck-us.net>
> > Cc: linux-hwmon@...r.kernel.org
> > Acked-by: Guenter Roeck <linux@...ck-us.net>
> > Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> 
> Not that it matters, but I keep wondering: Why don't people use auxiliary
> devices for situations like this, and keep the subsystem code where it
> belongs ?
> 

Good question. I haven't used auxiliary devices but did looks at it recently
when I stumbled across some x86 telemetry code just last week. I need to go
and understand it better to see how it can be used here as I don't have much
understanding ATM other than its uses in GPU and Audio subsystems.

> I am not requesting that you do it, I just wonder why the mechanism isn't
> used. I would have thought that it would be perfect for situations like
> this, so I guess I must be missing something, and I'd like to understand
> what that something is.
> 

Not sure, just that no one spent time think about it and see what is missing
if any and make it work.

-- 
Regards,
Sudeep