Re: [PATCH v6 4/9] i2c: refactor i2c_master_{send_recv}

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Sat, 4 Nov 2017 21:20:04 +0100
Wolfram Sang <wsa+renesas@sang-engineering.com> wrote:

> Those two functions are very similar, the only differences are that one
> needs the I2C_M_RD flag for its message while the other one needs the
> buffer casted to drop the const. Introduce a generic helper which
> allows to specify the flags (also needed later for DMA safe variants of
> these calls) and let the casting be done in the inlining fuctions which
> are now calling the new helper function.

The casting away of the const is a bit nasty, but short of making this
whole thing a macro, I can't see a better way.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  drivers/i2c/i2c-core-base.c | 64 +++++++++++++--------------------------------
>  include/linux/i2c.h         | 34 +++++++++++++++++++++---
>  2 files changed, 48 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index de1850bd440659..206c47c85c98c5 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -1972,63 +1972,35 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>  EXPORT_SYMBOL(i2c_transfer);
>  
>  /**
> - * i2c_master_send - issue a single I2C message in master transmit mode
> + * i2c_transfer_buffer_flags - issue a single I2C message transferring data
> + * 			       to/from a buffer
>   * @client: Handle to slave device
> - * @buf: Data that will be written to the slave
> - * @count: How many bytes to write, must be less than 64k since msg.len is u16
> + * @buf: Where the data is stored
> + * @count: How many bytes to transfer, must be less than 64k since msg.len is u16
> + * @flags: The flags to be used for the message, e.g. I2C_M_RD for reads
>   *
> - * Returns negative errno, or else the number of bytes written.
> + * Returns negative errno, or else the number of bytes transferred.
>   */
> -int i2c_master_send(const struct i2c_client *client, const char *buf, int count)
> +int i2c_transfer_buffer_flags(const struct i2c_client *client, char *buf,
> +			      int count, u16 flags)
>  {
>  	int ret;
> -	struct i2c_adapter *adap = client->adapter;
> -	struct i2c_msg msg;
> -
> -	msg.addr = client->addr;
> -	msg.flags = client->flags & I2C_M_TEN;
> -	msg.len = count;
> -	msg.buf = (char *)buf;
> -
> -	ret = i2c_transfer(adap, &msg, 1);
> -
> -	/*
> -	 * If everything went ok (i.e. 1 msg transmitted), return #bytes
> -	 * transmitted, else error code.
> -	 */
> -	return (ret == 1) ? count : ret;
> -}
> -EXPORT_SYMBOL(i2c_master_send);
> -
> -/**
> - * i2c_master_recv - issue a single I2C message in master receive mode
> - * @client: Handle to slave device
> - * @buf: Where to store data read from slave
> - * @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.
> - */
> -int i2c_master_recv(const struct i2c_client *client, char *buf, int count)
> -{
> -	struct i2c_adapter *adap = client->adapter;
> -	struct i2c_msg msg;
> -	int ret;
> -
> -	msg.addr = client->addr;
> -	msg.flags = client->flags & I2C_M_TEN;
> -	msg.flags |= I2C_M_RD;
> -	msg.len = count;
> -	msg.buf = buf;
> +	struct i2c_msg msg = {
> +		.addr = client->addr,
> +		.flags = flags | (client->flags & I2C_M_TEN),
> +		.len = count,
> +		.buf = buf,
> +	};
>  
> -	ret = i2c_transfer(adap, &msg, 1);
> +	ret = i2c_transfer(client->adapter, &msg, 1);
>  
>  	/*
> -	 * If everything went ok (i.e. 1 msg received), return #bytes received,
> -	 * else error code.
> +	 * If everything went ok (i.e. 1 msg transferred), return #bytes
> +	 * transferred, else error code.
>  	 */
>  	return (ret == 1) ? count : ret;
>  }
> -EXPORT_SYMBOL(i2c_master_recv);
> +EXPORT_SYMBOL(i2c_transfer_buffer_flags);
>  
>  /* ----------------------------------------------------
>   * the i2c address scanning function
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index a0b57de91e21d3..ef1a8791c1ae24 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -63,10 +63,36 @@ struct property_entry;
>   * transmit an arbitrary number of messages without interruption.
>   * @count must be be less than 64k since msg.len is u16.
>   */
> -extern int i2c_master_send(const struct i2c_client *client, const char *buf,
> -			   int count);
> -extern int i2c_master_recv(const struct i2c_client *client, char *buf,
> -			   int count);
> +extern int i2c_transfer_buffer_flags(const struct i2c_client *client,
> +				     char *buf, int count, u16 flags);
> +
> +/**
> + * i2c_master_recv - issue a single I2C message in master receive mode
> + * @client: Handle to slave device
> + * @buf: Where to store data read from slave
> + * @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(const struct i2c_client *client,
> +				  char *buf, int count)
> +{
> +	return i2c_transfer_buffer_flags(client, buf, count, I2C_M_RD);
> +};
> +
> +/**
> + * 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
> + * @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(const struct i2c_client *client,
> +				  const char *buf, int count)
> +{
> +	return i2c_transfer_buffer_flags(client, (char *)buf, count, 0);
> +};
>  
>  /* Transfer num messages.
>   */