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

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Message-ID: <20240220174624.GA27576@vamoiridPC>
Date: Tue, 20 Feb 2024 18:46:24 +0100
From: Vasileios Amoiridis <vassilisamir@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Vasileios Amoiridis <vassilisamir@...il.com>, 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 Tue, Feb 20, 2024 at 04:09:26PM +0200, Andy Shevchenko wrote:
> 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.
> 
> ...
> 

So you would suggest a re-ordering of the headers with a reverse
christmas-tree? I don't see it used in the other drivers of the IIO
subsystem but I can do it as well

> > +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
> 
>