linux-kernel - Re: [PATCH 4/4] hwmon: (oxp-sensors) Cache state of PWM enable mode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <28b7a9b2-a2ea-473e-8a17-2b987169b669@math.uni-bielefeld.de>
Date: Fri, 27 Dec 2024 00:13:40 +0100
From: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Derek John Clark <derekjohn.clark@...il.com>,
 Joaquín Ignacio Aramendía <samsagax@...il.com>,
 Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] hwmon: (oxp-sensors) Cache state of PWM enable mode

On 12/26/24 22:05, Guenter Roeck wrote:
> On Thu, Dec 26, 2024 at 06:00:19PM +0100, tjakobi@...h.uni-bielefeld.de wrote:
>> From: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
>>
>> The driver is in full control of the enable mode, so we
>> don't need to read it from HW every single time.
>>
> 
> That is not a reason for adding that much additional code.
> What is the problem that is being solved, and why is it worth that much
> additional code ?
I don't think it's that much additional code, but anyway: Reading from 
EC is not exactly fast, and I want this value cached for another reason. 
It turns out that some devices use a different scaling for the PWM value 
depending on whether the PWM is controlled automatically by the EC, or 
manually through the driver. And I don't want to do an additional EC 
read to figure this out, if I can avoid it.

With best wishes,
Tobias

> 
> Plus, again, all those runtime feature checks in attribute handling
> code are completely wrong.
> 
> Guenter