linux-kernel - Re: [PATCH v6 5/9] i2c: add i2c_master_{send|recv}

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Date:   Sat, 11 Nov 2017 00:08:50 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>
CC:     <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-renesas-soc@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <linux-input@...r.kernel.org>, <linux-media@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v6 5/9] i2c: add i2c_master_{send|recv}_dmasafe

On Sat, 4 Nov 2017 21:20:05 +0100
Wolfram Sang <wsa+renesas@...g-engineering.com> wrote:

> Use the new helper to create variants of i2c_master_{send|recv} which
> mark their buffers as DMA safe.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Can't really argue with such a simple patch ;)
Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  include/linux/i2c.h | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index ef1a8791c1ae24..8c144e3cbfb261 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -81,6 +81,22 @@ static inline int i2c_master_recv(const struct i2c_client *client,
>  };
>  
>  /**
> + * i2c_master_recv_dmasafe - issue a single I2C message in master receive mode
> + *			     using a DMA safe buffer
> + * @client: Handle to slave device
> + * @buf: Where to store data read from slave, must be safe to use with DMA
> + * @count: How many bytes to read, must be less than 64k since msg.len is u16
> + *
> + * Returns negative errno, or else the number of bytes read.
> + */
> +static inline int i2c_master_recv_dmasafe(const struct i2c_client *client,
> +					  char *buf, int count)
> +{
> +	return i2c_transfer_buffer_flags(client, buf, count,
> +					 I2C_M_RD | I2C_M_DMA_SAFE);
> +};
> +
> +/**
>   * i2c_master_send - issue a single I2C message in master transmit mode
>   * @client: Handle to slave device
>   * @buf: Data that will be written to the slave
> @@ -93,6 +109,21 @@ static inline int i2c_master_send(const struct i2c_client *client,
>  {
>  	return i2c_transfer_buffer_flags(client, (char *)buf, count, 0);
>  };
> +/**
> + * i2c_master_send_dmasafe - issue a single I2C message in master transmit mode
> + *			     using a DMA safe buffer
> + * @client: Handle to slave device
> + * @buf: Data that will be written to the slave, must be safe to use with DMA
> + * @count: How many bytes to write, must be less than 64k since msg.len is u16
> + *
> + * Returns negative errno, or else the number of bytes written.
> + */
> +static inline int i2c_master_send_dmasafe(const struct i2c_client *client,
> +					  const char *buf, int count)
> +{
> +	return i2c_transfer_buffer_flags(client, (char *)buf, count,
> +					 I2C_M_DMA_SAFE);
> +};
>  
>  /* Transfer num messages.
>   */