linux-kernel - Re: [PATCH 7/8] iio: adc: ad7476: Support ROHM BD79105

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aJO6jVcITlOXp0YB@smile.fi.intel.com>
Date: Wed, 6 Aug 2025 23:26:53 +0300
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/8] iio: adc: ad7476: Support ROHM BD79105

On Wed, Aug 06, 2025 at 10:04:43AM +0300, Matti Vaittinen wrote:
> The ROHM BD79105 is a simple 16-bit ADC accessible via SPI*.
> 
> The BD79105 has a CONVSTART pin, which must be set high to start the ADC
> conversion. Unlike with the ad7091 and ad7091r which also have a
> CONVSTART pin, the BD79105 requires that the pin must remain high also
> for the duration of the SPI access.
> 
> (*) Couple of words about the SPI. The BD79105 has pins named as
> CONVSTART, SCLK, DIN and DOUT. For the curious reader, DIN is not SPI
> ISO.
> 
> DIN is a signal which can be used as a chip-select. When DIN is pulled
> low, the ADC will output the completed measurement via DOUT as SCLK is
> clocked. According to the data-sheet, the DIN can also be used for
> daisy-chaining multiple ADCs. Also, DOUT can be used also for a
> 'data-ready' -IRQ. These modes aren't supported by this driver.
> 
> Support reading ADC scale and data from the BD79105 using SPI, when DIN
> is used as a chip-select.

...

> +static void bd79105_convst_disable(struct ad7476_state *st)
> +{
> +	if (!st->convst_gpio)
> +		return;

Dup code, please remove.

> +	gpiod_set_value(st->convst_gpio, 0);
> +}
> +
> +static void bd79105_convst_enable(struct ad7476_state *st)
> +{

> +	if (!st->convst_gpio)
> +		return;

With 10ns sleep in mind this is also unneeded check.

> +	gpiod_set_value(st->convst_gpio, 1);

> +	udelay(1); /* 10ns required for conversion */

We have ndelay(). But I believe toggling GPIO is much longer operation.

> +}

...

> @@ -347,7 +381,6 @@ static int ad7476_probe(struct spi_device *spi)
>  	if (st->convst_gpio)
>  		indio_dev->channels = st->chip_info->convst_channel;
>  	/* Setup default message */
> -
>  	st->xfer.rx_buf = &st->data;
>  	st->xfer.len = indio_dev->channels[0].scan_type.storagebits / 8;

Stray change.


-- 
With Best Regards,
Andy Shevchenko