Re: [PATCH v2] bus: fsl-mc: register the object drivers after misc_class exists

On Wed, Sep 09, 2026 at 07:04:40PM +0200, Vincent Jardin via B4 Relay wrote:

From: Vincent Jardin <vjardin@free.fr>

Unbinding and re-binding the root DPRC fails with:

  sysfs: cannot create duplicate filename '/dev/char/10:256'
    misc_register / fsl_mc_uapi_create_device_file /
    dprc_setup / dprc_probe

It happens when the fsl-mc bus probe is not deferred, without SMMU:
- the dprc driver is registered at postcore_initcall,
- the DT node is populated at arch_initcall_sync,
- the root DPRC probes right there, before misc_init() has
  registered misc_class at subsys_initcall.

misc_register() still succeeds but the device gets
no class, so misc_deregister() at unbind cannot find it:
the minor is freed while the device and its /sys/dev/char/ link leak,
and then the next bind collides on the same minor.

Let's move the dprc and allocator drivers registration, and
platform_driver_register(), to subsys_initcall_sync, after misc_init()
at subsys_initcall.
bus_register() and the platform-bus notifier stay at postcore_initcall
so that fsl_mc_bus_notifier() still pauses the MC before the SMMU is probed.

Thank you for the updated commit message.

Cc: stable+noautosel@kernel.org # niche: root DPRC unbind/rebind only
Fixes: 2cf1e703f066 ("bus: fsl-mc: add fsl-mc userspace support")
Signed-off-by: Vincent Jardin <vjardin@free.fr>

Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>