linux-kernel - Re: [PATCH] drivers: iio: pressure: Fixes BMP38x and BMP390 SPI support

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Date: Tue, 20 Feb 2024 16:09:26 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Vasileios Amoiridis <vassilisamir@...il.com>
Cc: jic23@...nel.org, lars@...afoo.de, ang.iglesiasg@...il.com,
	linus.walleij@...aro.org, semen.protsenko@...aro.org,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: iio: pressure: Fixes BMP38x and BMP390 SPI
 support

On Mon, Feb 19, 2024 at 08:13:59PM +0100, Vasileios Amoiridis wrote:
> According to the datasheet of BMP38x and BMP390 devices, for an SPI
> read operation the first byte that is returned needs to be dropped,
> and the rest of the bytes are the actual data returned from the
> sensor.

..

>  #include <linux/spi/spi.h>
>  #include <linux/err.h>
>  #include <linux/regmap.h>
> +#include <linux/bits.h>

I see that it's unsorted, but try to squeeze a new header to the better place
where more will be kept sorted. With given context, it should go before all
others, but it might be even better location.

..

> +static int bmp380_regmap_spi_read(void *context, const void *reg,
> +				  size_t reg_size, void *val, size_t val_size)
> +{
> +	struct spi_device *spi = to_spi_device(context);
> +	u8 rx_buf[4];
> +	ssize_t status;
> +
> +	/*
> +	 * Maximum number of consecutive bytes read for a temperature or
> +	 * pressure measurement is 3.
> +	 */
> +	if (val_size > 3)
> +		return -EINVAL;
> +	/*
> +	 * According to the BMP3xx datasheets, for a basic SPI read opertion,
> +	 * the first byte needs to be dropped and the rest are the requested
> +	 * data.
> +	 */
> +	status = spi_write_then_read(spi, reg, 1, rx_buf, val_size + 1);
> +	if (status)
> +		return status;

> +	memcpy(val, rx_buf + 1, val_size);

Okay, endianess is defined in the regmap_bus below...

> +	return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko