linux-kernel - RE: [PATCH v2] i3c: master: Add sysfs option to rescan bus.

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Message-ID:
 <SH0PR01MB08413FF4A5EDBFBF928A0B97F9952@SH0PR01MB0841.CHNPR01.prod.partner.outlook.cn>
Date: Sat, 24 Jan 2026 05:19:57 +0000
From: Joshua Yeong <joshua.yeong@...rfivetech.com>
To: Frank Li <Frank.li@....com>
CC: David Nyström <david.nystrom@....tech>, Alexandre
 Belloni <alexandre.belloni@...tlin.com>, "linux-i3c@...ts.infradead.org"
	<linux-i3c@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] i3c: master: Add sysfs option to rescan bus.

On Saturday, January 24, 2026 3:37 AM, Frank Li <Frank.li@....com> wrote:

> On Thu, Jan 22, 2026 at 06:08:29PM +0000, 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@....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 -> ...
>
> Look like this is more userful. The only do_daa() is not enough for rescan.
>
> Frank

If the other patch gets accepted ([PATCH V4 1/3] i3c: master: Add i3c_master_do_daa_ext() for post-hibernation address recovery)
Perhaps we can rename here to match what is being used there.

Joshua

> >
> > > Changes in v2:
> > > - Improved the commit message with "why".
> > > - Link to v1: 
> > > https://patch.msgid.link/20260122-i3c_rescan-v1-1-0c17071e232b@est.t
> > > ech
> > > ---
> > >  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@....tech>
> > >
> > >
> > > --
> > > linux-i3c mailing list
> > > linux-i3c@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-i3c

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