Re: [PATCH] nvme: hwmon: provide temperature min and max values for each sensor

From: Akinobu Mita <akinobu.mita@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-nvme@lists.infradead.org, linux-hwmon@vger.kernel.org,
	Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	Jean Delvare <jdelvare@suse.com>,
	Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH] nvme: hwmon: provide temperature min and max values for each sensor
Date: Tue, 12 Nov 2019 23:19:46 +0900	[thread overview]
Message-ID: <CAC5umyi97UJZzk+4soD+th0BZ71WfnOqnTWWuTYKyo6aWTdLXA@mail.gmail.com> (raw)
In-Reply-To: <20191111165306.GA19814@lst.de>

2019年11月12日(火) 1:53 Christoph Hellwig <hch@lst.de>:
>
> On Sun, Nov 10, 2019 at 11:17:46PM +0900, Akinobu Mita wrote:
> > +static int nvme_get_temp_thresh(struct nvme_ctrl *ctrl, int sensor, bool under,
> > +                             long *temp)
> > +{
> > +     unsigned int threshold = sensor << NVME_TEMP_THRESH_SELECT_SHIFT;
> > +     int status;
> > +     int ret;
> > +
> > +     if (under)
> > +             threshold |= NVME_TEMP_THRESH_TYPE_UNDER;
> > +
> > +     ret = nvme_get_features(ctrl, NVME_FEAT_TEMP_THRESH, threshold, NULL, 0,
> > +                             &status);
> > +     if (!ret)
> > +             *temp = ((status & NVME_TEMP_THRESH_MASK) - 273) * 1000;
> > +
> > +     return ret <= 0 ? ret : -EIO;
>
> This looks a little obsfucated.  aI'd prefer something like:
>
>         if (ret > 0)
>                 return -EIO;
>         if (ret < 0)
>                 return ret;
>         *temp = ((status & NVME_TEMP_THRESH_MASK) - 273) * 1000;
>         return 0;

Sounds good.

> > +     return ret <= 0 ? ret : -EIO;
>
> Similarly here, something like:
>
>         if (ret > 0)
>                 return -EIO;
>         return ret;

OK.

> > +             err = nvme_get_temp_thresh(data->ctrl, channel, false, val);
> > +             if (err)
> > +                     *val = (data->ctrl->wctemp - 273) * 1000;
>
> Can we have a helper for this (x - 273) * 1000 conversion?  It is
> repeated quite a bit over the code in this file.

OK. I'll add two macros.

#define MILLICELSIUS_TO_KELVIN(t) ((t) / 1000 + 273)
#define KELVIN_TO_MILLICELSIUS(t) (((t) - 273) * 1000)