linux-kernel - Re: [PATCH] lm75: add lm75b detection

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Message-ID: <20191028104618.5f21af38@endymion>
Date:   Mon, 28 Oct 2019 10:46:18 +0100
From:   Jean Delvare <jdelvare@...e.de>
To:     Rain Wang <Rain_Wang@...il.com>
Cc:     Guenter Roeck <linux@...ck-us.net>, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org
Subject: Re: [PATCH] lm75: add lm75b detection

On Sun, 27 Oct 2019 16:03:39 -0700, Guenter Roeck wrote:
> On 10/26/19 1:10 AM, Rain Wang wrote:
> > The National Semiconductor LM75B is very similar as the
> > LM75A, but it has no ID byte register 7, and unused registers
> > return 0xff rather than the last read value like LM75A.

Please send hwmon-related patches to the linux-hwmon list.

> > Signed-off-by: Rain Wang <rain_wang@...il.com>
> 
> I am quite hesitant to touch the detect function for this chip.
> Each addition increases the risk for false positives. What is the
> use case ?

I'm positively certain I don't want this. Ideally there should be no
detection at all for device without ID registers. The only reason there
are some occurrences of that is because there were no way to explicitly
instantiate I2C devices back then, and we have left the detection in
place to avoid perceived regressions. But today there are plenty of
ways to explicitly instantiate your I2C devices so there are no excuses
for more crappy detect functions. Ideally we would even get rid of
existing ones at some point in the future.

This patch is bad anyway as it only changes the device name without
implementing proper support for the LM75B.

-- 
Jean Delvare
SUSE L3 Support