Re: [PATCH V2 7/7] i3c: master: Reconcile dynamic addresses after DAA

[Frank Li <Frank.li@oss.nxp.com>]

On Tue, Jun 09, 2026 at 12:23:36PM +0300, Adrian Hunter wrote:
> On 08/06/2026 21:06, Frank Li wrote:
> > On Mon, Jun 08, 2026 at 10:58:00AM +0300, Adrian Hunter wrote:
> >> After Dynamic Address Assignment (DAA), there may be cases where
> >> devices have been assigned dynamic addresses on the bus, but are not
> >> successfully registered in the device model.  This can happen, for
> >> example, if errors occur during device addition, leaving the bus state
> >> and software state inconsistent.
> >>
> >> Introduce a reconciliation step to resolve such inconsistencies.
> >>
> >> Scan all address slots marked as I3C devices by the bus, and compare
> >> them against the set of devices currently registered.  For any dynamic
> >> address that is marked occupied but has no corresponding i3c_dev_desc,
> >> probe for device presence using a GETSTATUS CCC.
> >>
> >> Retry the probe (with exponential backoff delay) to handle transient NACK
> >> conditions.  If a device responds, register it via
> >> i3c_master_add_i3c_dev_locked().  Otherwise, free the address
> >> slot so it may be reused in future DAA operations.
> >>
> >> Note, i3c_master_add_i3c_dev_locked() may fail (again), in which case the
> >> dynamic address remains marked as occupied.  A future DAA will try again.
> >>
> >> This also handles a corner case where a device is assigned a dynamic
> >> address but not successfully added, and subsequently loses that address
> >> (e.g. due to power management).  If DAA is run again, the device may
> >> receive a new dynamic address while the old one remains marked as
> >> occupied.  Repeated occurrences of this scenario could eventually
> >> exhaust the dynamic address space.  The reconciliation step ensures that
> >> stale addresses are detected and freed, preventing address leakage.
> >>
> >> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> >> ---
...
> >> +
> >> +#define I3C_DEV_PROBE_INITIAL_DELAY_US	20
> >> +#define I3C_DEV_PROBE_DELAY_FACTOR	2
> >> +#define I3C_DEV_PROBE_CNT		5
>
> They are somewhat arbitrary, but should give a device enough
> opportunity to respond.

Need comments for it in case someone need adjust it in future. if spec
required, it can't change and need consider more.

>
> >
> > what's these value coming from? from i3c spec?
> >
...
>
> >> +	/* Reconcile the bitmap with the bus address slot status */
> >> +	for (unsigned int addr = 0; addr <= I2C_MAX_ADDR; addr++) {
> >> +		status = i3c_bus_get_addr_slot_status(&master->bus, addr);
> >> +		if (status != I3C_ADDR_SLOT_I3C_DEV || test_bit(addr, dev_dyn_addrs))
> >> +			continue;
> >> +		i3c_bus_set_addr_slot_status(&master->bus, addr, I3C_ADDR_SLOT_FREE);
> >> +		/* Try to add the device, but probe to see if it is really present */
> >> +		__i3c_master_add_i3c_dev_locked(master, addr, true);
> >
> > If dev add success for addr, but you free addr at previous line, any
> > issue?
>
> Currently, addr is always I3C_ADDR_SLOT_FREE on all paths that call
> __i3c_master_add_i3c_dev_locked(), so this is consistent.
>
> There is no i3c_dev_desc for this addr since that was checked just
> above.
>
> Then a success path will use i3c_master_attach_i3c_dev() which sets
> I3C_ADDR_SLOT_I3C_DEV via i3c_master_get_i3c_addrs()

Okay, I3C address allocate have little complex.

Frank


>
> >
> > Frank
> >> +	}
> >> +}
> >> +
> >>  /**
> >>   * i3c_master_do_daa_ext() - Dynamic Address Assignment (extended version)
> >>   * @master: controller
> >> @@ -2445,6 +2551,11 @@ int i3c_master_do_daa_ext(struct i3c_master_controller *master, bool rstdaa)
> >>  		if (rstdaa)
> >>  			rstret = i3c_master_rstdaa_locked(master, I3C_BROADCAST_ADDR);
> >>  		ret = master->ops->do_daa(master);
> >> +		/*
> >> +		 * Handle cases where a dynamic address was assigned but the
> >> +		 * device was not successfully added.
> >> +		 */
> >> +		i3c_master_reconcile_dyn_addrs(master);
> >>  	}
> >>
> >>  	i3c_bus_maintenance_unlock(&master->bus);
> >> --
> >> 2.51.0
> >>
>

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