[PATCH V3 3/7] i3c: master: Prevent reuse of dynamic address on device add failure

[Adrian Hunter]

i3c_master_add_i3c_dev_locked() is called after a device has already
been assigned a dynamic address.  If the function fails, the address
remains marked as free and may be reallocated to another device,
leading to address conflicts on the bus.

Ensure the address is not marked as free on failure, by updating the
address slot state to prevent the address from being re-used.

Emit an error message to inform of the failure.

Opportunistically remove the !master check because it is impossible.

Note, directly resetting the device's dynamic address is no longer
an option, since Direct RSTDAA was deprecated from I3C starting from
version 1.1 and v1.1 (or later) target devices are meant to NACK it.

Fixes: 3a379bbcea0af ("i3c: Add core I3C infrastructure")
Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
---


Changes in V3:

	Add note to commit message about Direct RSTDAA deprecation

Changes in V2:

	Fix 'if (IS_ERR(newdev)' error path.
	Be defensive and do not change the addr_slot_status if it is not
	free, and update commit message accordingly.
	Amend commit message to note removal of unnecesary 'if (!master)'
	check.
	Add Fixes tag.


 drivers/i3c/master.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index f87bf0099d3c..7b60b0c7f646 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -2345,12 +2345,11 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
 	bool enable_ibi = false;
 	int ret;
 
-	if (!master)
-		return -EINVAL;
-
 	newdev = i3c_master_alloc_i3c_dev(master, &info);
-	if (IS_ERR(newdev))
-		return PTR_ERR(newdev);
+	if (IS_ERR(newdev)) {
+		ret = PTR_ERR(newdev);
+		goto err_prevent_addr_reuse;
+	}
 
 	ret = i3c_master_attach_i3c_dev(master, newdev);
 	if (ret)
@@ -2472,6 +2471,16 @@ int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
 err_free_dev:
 	i3c_master_free_i3c_dev(newdev);
 
+err_prevent_addr_reuse:
+	/*
+	 * Although the device has not been added, the address has been
+	 * assigned. Prevent the address from being used again.
+	 */
+	if (i3c_bus_get_addr_slot_status(&master->bus, addr) == I3C_ADDR_SLOT_FREE)
+		i3c_bus_set_addr_slot_status(&master->bus, addr, I3C_ADDR_SLOT_I3C_DEV);
+
+	dev_err(&master->dev, "Failed to add I3C device at address %u, error %d\n", addr, ret);
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(i3c_master_add_i3c_dev_locked);
-- 
2.51.0