Re: [PATCH 4/8] i2c: rtl9300: introduce a property for 8 bit width reg address

[Chris Packham]

Hi Rustam,

(sorry I might have prematurely hit send on an earlier reply)

On 14/03/2026 21:26, Rustam Adilov wrote:
> In RTL9607C i2c controller, in order to indicate that the width of
> memory address is 8 bits, 0 is written to MEM_ADDR_WIDTH field as
> opposed to 1 for RTL9300 and RTL9310.
>
> Introduce a new property to a driver data to indicate what value
> need to written to MEM_ADDR_WIDTH field for this case.
>
> Signed-off-by: Rustam Adilov <adilov@xxxxxxxxxxx>
> ---
>   drivers/i2c/busses/i2c-rtl9300.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c
> index 2525b57a9d03..86a82f2c3ce0 100644
> --- a/drivers/i2c/busses/i2c-rtl9300.c
> +++ b/drivers/i2c/busses/i2c-rtl9300.c
> @@ -60,6 +60,7 @@ struct rtl9300_i2c_drv_data {
>   	u32 wd_reg;
>   	u8 max_nchan;
>   	u8 max_data_len;
> +	u8 reg_addr_8bit_len;
>   };
>   
>   #define RTL9300_I2C_MUX_NCHAN	8
> @@ -105,6 +106,7 @@ struct rtl9300_i2c_xfer {
>   #define RTL9300_I2C_MST_DATA_WORD2			0x10
>   #define RTL9300_I2C_MST_DATA_WORD3			0x14
>   #define RTL9300_I2C_MST_GLB_CTRL			0x384
> +#define RTL9300_REG_ADDR_8BIT_LEN			1
>   
>   #define RTL9310_I2C_MST_IF_CTRL				0x1004
>   #define RTL9310_I2C_MST_IF_SEL				0x1008
> @@ -299,6 +301,7 @@ static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned s
>   				  union i2c_smbus_data *data)
>   {
>   	struct rtl9300_i2c_chan *chan = i2c_get_adapdata(adap);
> +	const struct rtl9300_i2c_drv_data *drv_data;
>   	struct rtl9300_i2c *i2c = chan->i2c;
>   	struct rtl9300_i2c_xfer xfer = {0};
>   	int ret;
> @@ -308,6 +311,7 @@ static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned s
>   
>   	guard(rtl9300_i2c)(i2c);
>   
> +	drv_data = device_get_match_data(i2c->dev);
>   	ret = rtl9300_i2c_config_chan(i2c, chan);
>   	if (ret)
>   		return ret;
> @@ -315,7 +319,7 @@ static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned s
>   	xfer.dev_addr = addr & 0x7f;
>   	xfer.write = (read_write == I2C_SMBUS_WRITE);
>   	xfer.reg_addr = command;
> -	xfer.reg_addr_len = 1;
> +	xfer.reg_addr_len = drv_data->reg_addr_8bit_len;

For this one I wonder if we could come up with something that involves a 
subtraction for the rtl9607? len = 1 just makes sense to me so maybe 
RTL_9300_ADDR_LEN(1) which expands to 1 - 0 on the rtl9300 and 1 - 1 on 
the rtl9607 would be easier to follow.

Not a deal breaker just thought I'd mention it.

>   
>   	switch (size) {
>   	case I2C_SMBUS_BYTE:
> @@ -501,6 +505,7 @@ static const struct rtl9300_i2c_drv_data rtl9300_i2c_drv_data = {
>   	.wd_reg = RTL9300_I2C_MST_DATA_WORD0,
>   	.max_nchan = RTL9300_I2C_MUX_NCHAN,
>   	.max_data_len = RTL9300_I2C_MAX_DATA_LEN,
> +	.reg_addr_8bit_len = RTL9300_REG_ADDR_8BIT_LEN,
>   };
>   
>   static const struct rtl9300_i2c_drv_data rtl9310_i2c_drv_data = {
> @@ -524,6 +529,7 @@ static const struct rtl9300_i2c_drv_data rtl9310_i2c_drv_data = {
>   	.wd_reg = RTL9310_I2C_MST_DATA_CTRL,
>   	.max_nchan = RTL9310_I2C_MUX_NCHAN,
>   	.max_data_len = RTL9300_I2C_MAX_DATA_LEN,
> +	.reg_addr_8bit_len = RTL9300_REG_ADDR_8BIT_LEN,
>   };
>   
>   static const struct of_device_id i2c_rtl9300_dt_ids[] = {