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

[David Nyström]

On Thu, 22 Jan 2026, Joshua Yeong wrote:

> 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 -> ...

Are you referring to clarifying wording in the commit message, or the 
sysfs interface naming ?
What would be your suggestion, restore -> 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>
>>
>>
>> --
>> linux-i3c mailing list
>> linux-i3c at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-i3c
>