linux-kernel - Re: [PATCH 2/3] hwmon: (cros_ec) Add reading target fan RPM function

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Message-ID: <5cb816c0-c445-4a23-82de-e3d9cbce54ee@t-8ch.de>
Date: Fri, 14 Mar 2025 09:52:11 +0100
From: Thomas Weißschuh <thomas@...ssschuh.net>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Sung-Chi Li <lschyi@...omium.org>, Jean Delvare <jdelvare@...e.com>, 
	Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>, 
	chrome-platform@...ts.linux.dev, linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hwmon: (cros_ec) Add reading target fan RPM function

On 2025-03-13 16:36:54-0700, Guenter Roeck wrote:
> On 3/13/25 09:24, Thomas Weißschuh wrote:
> > On 2025-03-13 12:47:43+0800, Sung-Chi Li wrote:
> > > Implement the functionality of reading the target fan RPM setting from
> > > ChromeOS embedded controller under framework.
> > > 
> > > Signed-off-by: Sung-Chi Li <lschyi@...omium.org>
> > > ---
> > >   drivers/hwmon/cros_ec_hwmon.c | 18 ++++++++++++++++++
> > >   1 file changed, 18 insertions(+)
> > > 
> > > diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
> > > index b2fec0768301f116f49c57b8dbfb042b98a573e1..73bfcbbaf9531be6b753cfef8045fd5dab5b2ab3 100644
> > > --- a/drivers/hwmon/cros_ec_hwmon.c
> > > +++ b/drivers/hwmon/cros_ec_hwmon.c
> > > @@ -36,6 +36,19 @@ static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index
> > >   	return 0;
> > >   }
> > > +static int cros_ec_hwmon_read_fan_target(struct cros_ec_device *cros_ec, u8 index, int32_t *speed)
> > 
> > int32_t is a userspace type. In the kernel use i32, or even better u32.
> > 
> 
> Seems to be pretty widely used to complain about.

There is even a checkpatch.pl test for it, which should have triggered:
PREFER_KERNEL_TYPES.

> $ git grep int32_t drivers/ | wc
>   43662  192381 3555402

33k of those are in generated amdgpu headers.
This search also happens to include the more frequently used uint32_t.

> Also, in comparison:
> 
> $ git grep i32 drivers/ | wc
>     820    4009   68486

The numbers for u32 look a bit different:

$ git grep u32 drivers/ | wc
    234768 1137059 17410570


Also this specific driver already consistently uses uNN.
This does look wrong:

	int32_t target_rpm;
 	u16 speed;
 	u8 temp;


Thomas