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

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Message-ID: <Zc5D35_4FdERZXe4@smile.fi.intel.com>
Date: Thu, 15 Feb 2024 19:03:27 +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,
	579lpy@...il.com, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: iio: pressure: Add SPI support for BMP38x and
 BMP390

On Thu, Feb 15, 2024 at 05:43:32PM +0100, Vasileios Amoiridis wrote:
> According to the datasheet of BMP38x and BMP390 devices, in SPI
> operation, the first byte that returns after a read operation is
> garbage and it needs to be dropped and return the rest of the
> bytes.

Thank you for the patch, my comments below.

..

> +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 ret[BMP380_SPI_MAX_REG_COUNT_READ + 1];
> +	ssize_t status;
> +	u8 buf;

AFAIU this buffer is not DMA-capable.

> +	memcpy(&buf, reg, reg_size);

I prefer to see a switch case with cases based on allowed sizes and proper
endianess accessors.

> +	buf |= 0x80;

This is done by regmap, no?

> +	/*
> +	 * According to the BMP380, BMP388, BMP390 datasheets, for a basic
> +	 * read operation, after the write is done, 2 bytes are received and
> +	 * the first one has to be dropped. The 2nd one is the requested
> +	 * value.
> +	 */
> +	status = spi_write_then_read(spi, &buf, 1, ret, val_size + 1);

sizeof() ?

> +	if (status)
> +		return status;

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

As per above.

> +	return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko