linux-kernel - Re: [PATCH v10 6/8] iio: adc: Support ROHM BD79124 ADC

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Message-ID: <Z-EWmK2r6VgmPAqa@smile.fi.intel.com>
Date: Mon, 24 Mar 2025 10:23:52 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>, Nuno Sa <nuno.sa@...log.com>,
	David Lechner <dlechner@...libre.com>,
	Javier Carrasco <javier.carrasco.cruz@...il.com>,
	Olivier Moysan <olivier.moysan@...s.st.com>,
	Guillaume Stols <gstols@...libre.com>,
	Dumitru Ceclan <mitrutzceclan@...il.com>,
	Trevor Gamblin <tgamblin@...libre.com>,
	Matteo Martelli <matteomartelli3@...il.com>,
	Alisa-Dariana Roman <alisadariana@...il.com>,
	João Paulo Gonçalves <joao.goncalves@...adex.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v10 6/8] iio: adc: Support ROHM BD79124 ADC

On Mon, Mar 24, 2025 at 09:13:42AM +0200, Matti Vaittinen wrote:
> The ROHM BD79124 is a 12-bit, 8-channel, SAR ADC. The ADC supports
> an automatic measurement mode, with an alarm interrupt for out-of-window
> measurements. The window is configurable for each channel.
> 
> The I2C protocol for manual start of the measurement and data reading is
> somewhat peculiar. It requires the master to do clock stretching after
> sending the I2C slave-address until the slave has captured the data.
> Needless to say this is not well suopported by the I2C controllers.
> 
> Thus do not support the BD79124's manual measurement mode but implement
> the measurements using automatic measurement mode, relying on the
> BD79124's ability of storing latest measurements into register.
> 
> Support also configuring the threshold events for detecting the
> out-of-window events.
> 
> The BD79124 keeps asserting IRQ for as long as the measured voltage is
> out of the configured window. Thus, prevent the user-space from choking
> on the events and mask the received event for a fixed duration (1 second)
> when an event is handled.
> 
> The ADC input pins can be also configured as general purpose outputs.
> Make those pins which don't have corresponding ADC channel node in the
> device-tree controllable as GPO.

Thank you for the nicely written driver!
However, I have one big issue with it (see below).

...

> +static void bd79124gpo_set(struct gpio_chip *gc, unsigned int offset, int value)
> +static void bd79124gpo_set_multiple(struct gpio_chip *gc, unsigned long *mask,
> +				    unsigned long *bits)

These will be _rv variants anyway as there is no chance this series goes before that.

...

> +struct bd79124_raw {
> +	u8 val_bit3_0; /* Is set in high bits of the byte */
> +	u8 val_bit11_4;
> +};
> +#define BD79124_RAW_TO_INT(r) ((r.val_bit11_4 << 4) | (r.val_bit3_0 >> 4))
> +#define BD79124_INT_TO_RAW(val) {					\
> +	.val_bit11_4 = (val) >> 4,					\
> +	.val_bit3_0 = (val) << 4,					\
> +}

All the rest is fine to me and looks good, but above is a principal impediment
to give you my tag. In case you update the type to __le16, feel free to add
my Reviewed-by tag.

-- 
With Best Regards,
Andy Shevchenko