linux-kernel - Re: [PATCH v4 4/7] iio: pressure: bmp280: Use sleep and forced mode for oneshot captures

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Message-ID: <ZtDZWCgE-zRriyQ4@smile.fi.intel.com>
Date: Thu, 29 Aug 2024 23:26:00 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: jic23@...nel.org, lars@...afoo.de, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, ang.iglesiasg@...il.com,
	linus.walleij@...aro.org, biju.das.jz@...renesas.com,
	javier.carrasco.cruz@...il.com, semen.protsenko@...aro.org,
	579lpy@...il.com, ak@...klinger.de, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	christophe.jaillet@...adoo.fr
Subject: Re: [PATCH v4 4/7] iio: pressure: bmp280: Use sleep and forced mode
 for oneshot captures

On Thu, Aug 29, 2024 at 09:13:44PM +0200, Vasileios Amoiridis wrote:
> On Thu, Aug 29, 2024 at 03:31:48PM +0300, Andy Shevchenko wrote:
> > On Wed, Aug 28, 2024 at 10:51:24PM +0200, Vasileios Amoiridis wrote:

...

> > int bmp280_chip_config(struct bmp280_data *data)
> > 
> > >  				BMP280_OSRS_TEMP_MASK |
> > >  				BMP280_OSRS_PRESS_MASK |
> > >  				BMP280_MODE_MASK,
> > > -				osrs | BMP280_MODE_NORMAL);
> > > +				osrs | BMP280_MODE_SLEEP);
> > >  	if (ret) {
> > >  		dev_err(data->dev, "failed to write ctrl_meas register\n");
> > >  		return ret;
> > 
> > This _feels_ like a separate change. I haven't found anything explicitly
> > describing it in the commit message. Did I miss it?
> 
> Well this change is because before, the sensor was by default in
> NORMAL_MODE so whenever we were writing a different setting (Output
> data rate, oversampling ratio) to the sensor, the NORMAL_MODE was
> chosen. There was no idea of SLEEP or FORCED MODE.
> 
> While now, since this commits adds the idea of SLEEP_MODE
> by default (FORCED_MODE for oneshot captures, and NORMAL_MODE for
> buffer/trigger) we need to keep the sensor in SLEEP_MODE as well
> when we change its configuration.
> 
> I believe it belongs to this commit. Maybe though, I should mention
> this change explicitly in the commit message?

Yes, please.

...

> > And in programming hardware we quite often operate with power-of-2 things, so I
> > recommend to have 8 per line,
> > 
> > 	static const int time_conv_press[] = {
> > 		0, 1050, 1785, 3045, 5670, 10920, 21420, 42420,		/* 0-7 */
> > 		84420,							/* 8 */
> > 	};
> 
> I was not aware of this convention, I can do it.

It's rather a common sense to easy maintain this and see exactly how many
(decimal) values are supplied. With hex values we usually make them fixed-width
and hence easier to count (however also makes sense to keep power-of-2 in mind).

-- 
With Best Regards,
Andy Shevchenko