linux-kernel - Re: [PATCH v2] hwmon (max6639): Use regmap

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

Message-ID: <af66ac87-32ff-48a6-bf1c-d7ac578ceb4c@roeck-us.net>
Date: Thu, 2 May 2024 11:22:40 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Naresh Solanki <naresh.solanki@...ements.com>
Cc: Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] hwmon (max6639): Use regmap

On 5/2/24 10:25, Naresh Solanki wrote:
[ ... ]

>>> +     u8 pwm[MAX6639_NDEV];           /* Register value: Duty cycle 0..120 */
>>
>> pwm caching needs to be dropped as well. It is no longer initialized in
>> max6639_init_client(), but updated and later used in pwm_store() and
>> pwm_show(). Looking at the datasheet, the pwm registers are volatile
>> and should not be cached in the first place.
> Yes. I did that but found that the register is write only. i.e.,

Odd. The datasheet says that it is r/w or, rather, that reading it returns
the _current_ pwm value and writing it sets the target pwm value in pwm mode.

What happens when the register is read ?

Thanks,
Guenter