linux-kernel - Re: [RFC PATCH] imx-i2c: Add smbus block read support to imx i2c bus

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Date:	Wed, 2 Apr 2014 16:30:47 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Kaushal Butala <kaushalkernelmailinglist@...il.com>
CC:	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Kaushal Butala <kaushal.butala@...il.com>,
	Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [RFC PATCH] imx-i2c: Add smbus block read support to imx i2c bus

On Tue, Mar 25, 2014 at 04:06:22PM +0100, Kaushal Butala wrote:
> From: Kaushal Butala <kaushal.butala@...il.com>
> 
> The smbus block read is not currently supported for imx i2c devices.
> This patchset adds the support to imx i2c bus so that blocks of data
> can be read using SMbus block reads.(using i2c_smbus_read_block_data()
> function from the i2c_core.c.). Tested with 3.10.9 kernel.
> 
> Signed-off-by: Kaushal Butala <kaushalkernelmailinglist@...il.com>

The patch should be sent to I2C subsystem maintainer - Wolfram (copied)
rather than me.

The patch looks good to me except a few unnecessary parentheses.

> ---
>  drivers/i2c/busses/i2c-imx.c |   31 ++++++++++++++++++++++++++++---
>  1 file changed, 28 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index db895fb..b6c2c3c 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -462,6 +462,7 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
>  {
>  	int i, result;
>  	unsigned int temp;
> +	int block_data = msgs->flags & I2C_M_RECV_LEN;
>  
>  	dev_dbg(&i2c_imx->adapter.dev,
>  		"<%s> write slave address: addr=0x%x\n",
> @@ -481,7 +482,12 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
>  	/* setup bus to read data */
>  	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
>  	temp &= ~I2CR_MTX;
> -	if (msgs->len - 1)
> +
> +	/*
> +	 * Reset the I2CR_TXAK flag initially for SMbus block read since the
> +	 * length is unknown
> +	 */
> +	if ((msgs->len - 1) || (block_data))

Unnecessary parentheses around block_data.

>  		temp &= ~I2CR_TXAK;
>  	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
>  	imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
> @@ -490,9 +496,24 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
>  
>  	/* read data */
>  	for (i = 0; i < msgs->len; i++) {
> +		u8 len = 0;
>  		result = i2c_imx_trx_complete(i2c_imx);
>  		if (result)
>  			return result;
> +		/*
> +		 * First byte is the length of remaining packet
> +		 * in the SMBus block data read. Add it to
> +		 * msgs->len.
> +		 */
> +		if ((!i) && (block_data)) {

if (!i && block_data)

> +			len = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
> +			if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX))
> +				return -EPROTO;
> +			dev_dbg(&i2c_imx->adapter.dev,
> +				"<%s> read length: 0x%X\n",
> +				__func__, len);
> +			msgs->len += len;
> +		}
>  		if (i == (msgs->len - 1)) {
>  			/* It must generate STOP before read I2DR to prevent
>  			   controller from generating another clock cycle */
> @@ -510,7 +531,10 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
>  			temp |= I2CR_TXAK;
>  			imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
>  		}
> -		msgs->buf[i] = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
> +		if ((!i) && (block_data))

Ditto

Shawn

> +			msgs->buf[0] = len;
> +		else
> +			msgs->buf[i] =  imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
>  		dev_dbg(&i2c_imx->adapter.dev,
>  			"<%s> read byte: B%d=0x%X\n",
>  			__func__, i, msgs->buf[i]);
> @@ -583,7 +607,8 @@ fail0:
>  
>  static u32 i2c_imx_func(struct i2c_adapter *adapter)
>  {
> -	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
> +		| I2C_FUNC_SMBUS_READ_BLOCK_DATA;
>  }
>  
>  static struct i2c_algorithm i2c_imx_algo = {
> -- 
> 1.7.9.5
> 
> 
> 

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