Add the ability to rescan the i3c bus from userspace, i.e. provoke
an ENTDDA. 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@est.tech>
---
Changes in v3:
- Rename sysfs entry from rescan to entdda, Comment: Joshua Yeong
- Link to v2: https://patch.msgid.link/20260122-i3c_rescan-v2-1-84c74a483f03@est.tech

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..a1d816634a25 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 entdaa_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(entdaa);
+
 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_entdaa.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(i3c_masterdev);

---
base-commit: e3b32dcb9f23e3c3927ef3eec6a5842a988fb574
change-id: 20260116-i3c_rescan-4921d0b41a00

Best regards,
--  
David Nyström <david.nystrom@est.tech>

On Fri, Jan 23, 2026 at 08:55:37AM +0100, David Nyström wrote:
> Add the ability to rescan the i3c bus from userspace, i.e. provoke
> an ENTDDA. 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.

AI helpped rephrase

Allow userspace to request a dynamic address assignment, which is
useful for devices with broken hot-join support or devices that boot
slowly and may miss the initial DDA during system startup.

Need update ABI document

Documentation/ABI/testing/sysfs-bus-i3c

Frank
>
> Signed-off-by: David Nyström <david.nystrom@est.tech>
> ---
> Changes in v3:
> - Rename sysfs entry from rescan to entdda, Comment: Joshua Yeong
> - Link to v2: https://patch.msgid.link/20260122-i3c_rescan-v2-1-84c74a483f03@est.tech
>
> 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..a1d816634a25 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 entdaa_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(entdaa);
> +
>  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_entdaa.attr,
>  	NULL,
>  };
>  ATTRIBUTE_GROUPS(i3c_masterdev);
>
> ---
> base-commit: e3b32dcb9f23e3c3927ef3eec6a5842a988fb574
> change-id: 20260116-i3c_rescan-4921d0b41a00
>
> Best regards,
> --
> David Nyström <david.nystrom@est.tech>
>