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

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Message-ID: <0be30d7d-f091-4497-bb72-fdcad276285e@roeck-us.net>
Date: Fri, 11 Apr 2025 07:15:22 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Sudeep Holla <sudeep.holla@....com>
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 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 ?

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.

Thanks,
Guenter