linux-kernel - Re: [PATCH 6/7] hwmon: iio: Add min/max support

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Message-ID: <20250729193723.5f0d784e@jic23-huawei>
Date: Tue, 29 Jul 2025 19:37:23 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>,
 linux-iio@...r.kernel.org, linux-hwmon@...r.kernel.org, Andy Shevchenko
 <andy@...nel.org>, Nuno Sá <nuno.sa@...log.com>,
 linux-kernel@...r.kernel.org, David Lechner <dlechner@...libre.com>
Subject: Re: [PATCH 6/7] hwmon: iio: Add min/max support

On Mon, 28 Jul 2025 18:32:43 -0400
Sean Anderson <sean.anderson@...ux.dev> wrote:

> On 7/27/25 12:35, Jonathan Cameron wrote:
> > On Mon, 14 Jul 2025 21:20:22 -0400
> > Sean Anderson <sean.anderson@...ux.dev> wrote:
> >   
> >> Add support for minimum/maximum attributes. Like the _input attribute,
> >> we just need to call into the IIO API.
> >> 
> >> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>  
> > 
> > Similar comments to previous. I'm not keen on the blend of allocation of
> > attributes and registration.  If we can break that link I think it will give
> > cleaner code.
> >  
> >>  static int add_device_attr(struct device *dev, struct iio_hwmon_state *st,
> >>  			   ssize_t (*show)(struct device *dev,
> >>  					   struct device_attribute *attr,
> >> @@ -123,6 +171,40 @@ static int add_device_attr(struct device *dev, struct iio_hwmon_state *st,
> >>  	return 0;
> >>  }
> >>  
> >> +static int add_event_attr(struct device *dev, struct iio_hwmon_state *st,
> >> +			  int i, enum iio_event_direction dir,
> >> +			  const char *fmt, ...)
> >> +{
> >> +	struct sensor_device_attribute_2 *a;
> >> +	umode_t mode;
> >> +	va_list ap;
> >> +
> >> +	mode = iio_event_mode(&st->channels[i], IIO_EV_TYPE_THRESH, dir,
> >> +			      IIO_EV_INFO_VALUE);
> >> +	if (!mode)
> >> +		return 0;
> >> +
> >> +	a = devm_kzalloc(dev, sizeof(*a), GFP_KERNEL);
> >> +	if (!a)
> >> +		return -ENOMEM;
> >> +
> >> +	sysfs_attr_init(&a->dev_attr.attr);
> >> +	va_start(ap, fmt);
> >> +	a->dev_attr.attr.name = devm_kvasprintf(dev, GFP_KERNEL, fmt, ap);
> >> +	va_end(ap);
> >> +	if (!a->dev_attr.attr.name)
> >> +		return -ENOMEM;
> >> +
> >> +	a->dev_attr.show = iio_hwmon_read_event;
> >> +	a->dev_attr.store = iio_hwmon_write_event;
> >> +	a->dev_attr.attr.mode = mode;
> >> +	a->index = i;
> >> +	a->nr = dir;
> >> +
> >> +	st->attrs[st->num_attrs++] = &a->dev_attr.attr;  
> > similar comment to the previous, though here I think we'd
> > need to pass in the channel to an iio_hwmon_alloc_event_attr() as ideally we'd
> > not be messing with st at all in here.  So maybe it doesn't work out.  
> 
> Well, I used to have
> 
> +               if (iio_read_channel_label(&st->channels[i], buf) >= 0) {
> +                       st->attrs[attr] = create_attr(dev, iio_hwmon_read_label,
> +                                                     NULL, 0444, i, 0, 0, 0,
> +                                                     "%s%d_label", prefix, n);
> +                       if (!st->attrs[attr++])
pushing attr off the end is not a good idea even if we know we don't use it
any more.
> +                               return -ENOMEM;
> +               }
> 
> but even with a shorter function name, all the parameters are starting
> to get bunched up on the right side. And if we make it longer as you
> propose it starts looking like
Using a local variable
			struct attribute *att;

			att = create_attr(dev, iio_hwmon_read_lanel,
					 ...
			if (!att)
				return -ENOMEM;

			st->attrs[attr++] = att;
helps but still ugly.
> 
> 
> +               if (iio_read_channel_label(&st->channels[i], buf) >= 0) {
> +                       st->attrs[attr] =
> +                               iio_hwmon_create_device_attr(dev,
> +                                                            iio_hwmon_read_label,
> +                                                            NULL, 0444, i, 0, 0,
> +                                                            0, "%s%d_label",
> +                                                            prefix, n);
> +                       if (!st->attrs[attr++])
> +                               return -ENOMEM;
> +               }
> 
> which is IMO really terrible-looking.

Fair enough. let's leave it as is.
> 
> Maybe we should just stick everything in an xarray and linearize it at
> the end of probe...
If it looks nicer - feel free!

J
> 
> --Sean