linux-kernel - Re: [bug report] iio: dac: adding support for Microchip MCP47FEB02

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Message-ID: <aYYFba5-ZV8VuZHM@smile.fi.intel.com>
Date: Fri, 6 Feb 2026 17:14:53 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Ariana Lazar <ariana.lazar@...rochip.com>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>, linux-iio@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [bug report] iio: dac: adding support for Microchip MCP47FEB02

On Fri, Feb 06, 2026 at 05:33:26PM +0300, Dan Carpenter wrote:
> On Fri, Feb 06, 2026 at 04:04:07PM +0200, Andy Shevchenko wrote:
> > > drivers/iio/dac/mcp47feb02.c
> > >     712 static int mcp47feb02_init_scales_avail(struct mcp47feb02_data *data, int vdd_mV,
> > >     713                                         int vref_mV, int vref1_mV)
> > >     714 {
> > >     715         struct device *dev = regmap_get_device(data->regmap);
> > >     716         int tmp_vref;
> > >     717 
> > >     718         mcp47feb02_init_scale(data, MCP47FEB02_SCALE_VDD, vdd_mV, data->scale);
> > >     719 
> > >     720         if (data->use_vref)
> > >     721                 tmp_vref = vref_mV;
> > >     722         else
> > >     723                 tmp_vref = MCP47FEB02_INTERNAL_BAND_GAP_mV;
> > >     724 
> > >     725         mcp47feb02_init_scale(data, MCP47FEB02_SCALE_GAIN_X1, tmp_vref, data->scale);
> > >     726         mcp47feb02_init_scale(data, MCP47FEB02_SCALE_GAIN_X2, tmp_vref * 2, data->scale);
> > >     727 
> > >     728         if (data->phys_channels >= 4) {
> > >     729                 mcp47feb02_init_scale(data, MCP47FEB02_SCALE_VDD, vdd_mV, data->scale_1);
> > >     730 
> > >     731                 if (data->use_vref1 && vref1_mV <= 0)
> > > --> 732                         return dev_err_probe(dev, vref1_mV, "Invalid voltage for Vref1\n");
> > >                                                           ^^^^^^^^
> > > vref1_mV is not a valid error code.
> > 
> > Why not? When it's negative I believe the above statement is not true.
> 
> I saw this as just sanity checking the input.  vref1_mV is never
> actually negative.  I don't know if devm_regulator_get_enable_read_voltage()
> can return less than one millivolt.

 * In cases where the supply is not strictly required, callers can check for
 * -ENODEV error and handle it accordingly.
 *
 * Returns: voltage in microvolts on success, or an negative error number on failure.

What did I miss?

-- 
With Best Regards,
Andy Shevchenko