Re: [PATCH RFC] eeprom: ee1004: add support for temperature sensor

[Heiner Kallweit <hkallweit1@gmail.com>]

On 15.11.2023 12:17, Heiner Kallweit wrote:
> Jean and me are discussing how to best instantiate temperature sensors
> that can be found on RAM modules. First idea was to extend
> i2c_register_spd() but I think reading the "temp sensor present" flag
> from SPD can't be properly done from an i2c core level.
> Therefore, for DDR4, do it from the ee1004 driver.
> 
> The temp sensor i2c address can be derived from the SPD i2c address,
> so I think we can directly instantiate the device and don't have to
> probe for it.
> If the temp sensor has been instantiated already by other means
> (e.g. class-based auto-detection), then the busy-check in 
> i2c_new_client_device will detect this.
> 
> Link: https://www.spinics.net/lists/linux-i2c/msg65963.html
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  drivers/misc/eeprom/ee1004.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/misc/eeprom/ee1004.c b/drivers/misc/eeprom/ee1004.c
> index a1acd7713..4bce8f9d9 100644
> --- a/drivers/misc/eeprom/ee1004.c
> +++ b/drivers/misc/eeprom/ee1004.c
> @@ -158,6 +158,22 @@ static struct bin_attribute *ee1004_attrs[] = {
>  
>  BIN_ATTRIBUTE_GROUPS(ee1004);
>  
> +static void ee1004_probe_temp_sensor(struct i2c_client *client)
> +{
> +	struct i2c_board_info info = { .type = "jc42" };
> +	u8 byte14;
> +	int ret;
> +
> +	/* byte 14, bit 7 is set if temp sensor is present */
> +	ret = ee1004_eeprom_read(client, &byte14, 14, 1);
> +	if (ret != 1 || !(byte14 & BIT(7)))
> +		return;
> +
> +	info.addr = 0x18 | (client->addr & 7);
> +
> +	i2c_new_client_device(client->adapter, &info);
> +}
> +
>  static void ee1004_cleanup(int idx)
>  {
>  	if (--ee1004_dev_count == 0)
> @@ -204,6 +220,9 @@ static int ee1004_probe(struct i2c_client *client)
>  		err = -EOPNOTSUPP;
>  		goto err_clients;
>  	}
> +
> +	ee1004_probe_temp_sensor(client);
> +
>  	mutex_unlock(&ee1004_bus_lock);
>  
>  	dev_info(&client->dev,

Jean, do you have any feedback on this one?
Also not sure why this patch is marked "superseded" in patchwork.