linux-kernel - Re: [PATCH v3 3/6] regmap: Add regmap_noinc

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Date:   Mon, 6 Aug 2018 11:25:08 +0100
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Stefan Popa <stefan.popa@...log.com>
CC:     <jic23@...nel.org>, <broonie@...nel.org>, <lars@...afoo.de>,
        <Michael.Hennerich@...log.com>, <knaack.h@....de>,
        <pmeerw@...erw.net>, <mark.rutland@....com>, <davem@...emloft.net>,
        <mchehab+samsung@...nel.org>, <gregkh@...uxfoundation.org>,
        <akpm@...ux-foundation.org>, <robh+dt@...nel.org>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        "Crestez Dan Leonard" <leonard.crestez@...el.com>
Subject: Re: [PATCH v3 3/6] regmap: Add regmap_noinc_read API

On Fri, Aug 03, 2018 at 04:02:18PM +0300, Stefan Popa wrote:
> From: Crestez Dan Leonard <leonard.crestez@...el.com>
> 
> The regmap API usually assumes that bulk read operations will read a
> range of registers but some I2C/SPI devices have certain registers for
> which a such a read operation will return data from an internal FIFO
> instead. Add an explicit API to support bulk read without range semantics.
> 
> Some linux drivers use regmap_bulk_read or regmap_raw_read for such
> registers, for example mpu6050 or bmi150 from IIO. This only happens to
> work because when caching is disabled a single regmap read op will map
> to a single bus read op (as desired). This breaks if caching is enabled and
> reg+1 happens to be a cacheable register.
> 
> Without regmap support refactoring a driver to enable regmap caching
> requires separate I2C and SPI paths. This is exactly what regmap is
> supposed to help avoid.
> 
> Suggested-by: Jonathan Cameron <jic23@...nel.org>
> Signed-off-by: Crestez Dan Leonard <leonard.crestez@...el.com>
> Signed-off-by: Stefan Popa <stefan.popa@...log.com>
> ---
> diff --git a/include/linux/regmap.h b/include/linux/regmap.h
> index 4f38068..b6e6040 100644
> --- a/include/linux/regmap.h
> +++ b/include/linux/regmap.h
> @@ -946,6 +946,8 @@ int regmap_raw_write_async(struct regmap *map, unsigned int reg,
>  int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val);
>  int regmap_raw_read(struct regmap *map, unsigned int reg,
>  		    void *val, size_t val_len);
> +int regmap_noinc_read(struct regmap *map, unsigned int reg,
> +		      void *val, size_t val_len);
>  int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val,
>  		     size_t val_count);
>  int regmap_update_bits_base(struct regmap *map, unsigned int reg,
> @@ -1196,6 +1198,13 @@ static inline int regmap_raw_read(struct regmap *map, unsigned int reg,
>  	return -EINVAL;
>  }
>  
> +static inline int regmap_pipe_read(struct regmap *map, unsigned int reg,
> +				   void *val, size_t val_len)
> +{
> +	WARN_ONCE(1, "regmap API is disabled");
> +	return -EINVAL;
> +}
> +

This is presumably supposed to be regmap_noinc_read.

Thanks,
Charles