[PATCH v2] i3c: master: Add sysfs option to rescan bus.

[Joshua Yeong]

On Friday, January 23, 2026 1:58 AM, David Nyström wrote:

> Add the ability to rescan the i3c bus from userspace, i.e. provoke a DDA.
> The usecase could be f.ex. an i3cdev userspace driver for a device with broken hotjoin support. If the i3c device boots slowly, it might be miss the DDA during boot.
>
> Signed-off-by: David Nyström <david.nystrom at est.tech>
> ---

Can we rename rescan to something where indicate we are only doing ENTDAA? I think rescan keyword should be reserved for complete rescan of i3c bus.
DISEC -> RSTDAA -> ENTDAA -> ...

> Changes in v2:
> - Improved the commit message with "why".
> - Link to v1: https://patch.msgid.link/20260122-i3c_rescan-v1-1-0c17071e232b@est.tech
> ---
>  drivers/i3c/master.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c index 80dda0e85558..edeae7493b3b 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -758,6 +758,29 @@ static ssize_t dev_nack_retry_count_store(struct device *dev,
>
>  static DEVICE_ATTR_RW(dev_nack_retry_count);
>
> +static ssize_t rescan_store(struct device *dev,
> +			    struct device_attribute *attr,
> +			    const char *buf, size_t count)
> +{
> +	struct i3c_master_controller *master = dev_to_i3cmaster(dev);
> +	unsigned long val;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val) {
> +		ret = i3c_master_do_daa(master);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return count;
> +}
> +
> +static DEVICE_ATTR_WO(rescan);
> +
>  static struct attribute *i3c_masterdev_attrs[] = {
>  	&dev_attr_mode.attr,
>  	&dev_attr_current_master.attr,
> @@ -769,6 +792,7 @@ static struct attribute *i3c_masterdev_attrs[] = {
>  	&dev_attr_dynamic_address.attr,
>  	&dev_attr_hdrcap.attr,
>  	&dev_attr_hotjoin.attr,
> +	&dev_attr_rescan.attr,
>  	NULL,
>  };
>  ATTRIBUTE_GROUPS(i3c_masterdev);
>
> ---
> base-commit: e3b32dcb9f23e3c3927ef3eec6a5842a988fb574
> change-id: 20260116-i3c_rescan-4921d0b41a00
>
> Best regards,
> --
> David Nyström <david.nystrom at est.tech>
>
>
> --
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