Hi Tomas, FYI, this commit triggers a boot time warning. tree: git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-next head: 6915c0e487c822e2436683e14302c0b8a6155cc7 commit: 6915c0e487c822e2436683e14302c0b8a6155cc7 [1/1] tty: uartclk value from serial_core exposed to sysfs [ 1.882306] [] ? put_device+0xf/0x20 [ 1.883140] [] put_device+0xf/0x20 [ 1.884821] [] tty_unregister_device+0x26/0x50 [ 1.875434] PM: Removing info for No Bus:ttyS0 [ 1.876344] ------------[ cut here ]------------ [ 1.876762] WARNING: at /c/kernel-tests/src/stable/drivers/base/core.c:196 device_release+0x6e/0x80() [ 1.877550] Device 'ttyS0' does not have a release() function, it is broken and must be fixed. [ 1.878247] Modules linked in: [ 1.878552] Pid: 1, comm: swapper/0 Not tainted 3.6.0-rc3-00189-g6915c0e #176 [ 1.879209] Call Trace: [ 1.879419] [] warn_slowpath_common+0x5f/0x80 [ 1.879861] [] ? device_release+0x6e/0x80 [ 1.880268] [] ? device_release+0x6e/0x80 [ 1.880682] [] warn_slowpath_fmt+0x2e/0x30 [ 1.881090] [] device_release+0x6e/0x80 [ 1.881479] [] kobject_cleanup+0x36/0x80 [ 1.881942] [] kobject_put+0x25/0x60 [ 1.882306] [] ? put_device+0xf/0x20 [ 1.882746] [] ? device_del+0x12c/0x160 [ 1.883140] [] put_device+0xf/0x20 [ 1.883551] [] device_unregister+0x36/0x50 [ 1.883963] [] device_destroy+0x2d/0x40 [ 1.884346] [] ? class_dir_child_ns_type+0x10/0x10 [ 1.884821] [] tty_unregister_device+0x26/0x50 [ 1.885314] [] uart_remove_one_port+0x82/0xf0 [ 1.885830] [] serial8250_register_8250_port+0x6d/0x280 [ 1.886321] [] ? check_name+0x2f/0x2f [ 1.886711] [] serial_pnp_probe+0x166/0x1ff [ 1.887126] [] pnp_device_probe+0x57/0xc0 [ 1.887592] [] driver_probe_device+0xdb/0x2e0 [ 1.888020] [] __driver_attach+0x91/0xa0 [ 1.888403] [] ? driver_probe_device+0x2e0/0x2e0 [ 1.888864] [] bus_for_each_dev+0x38/0x70 [ 1.889269] [] driver_attach+0x19/0x20 [ 1.889721] [] ? driver_probe_device+0x2e0/0x2e0 [ 1.890157] [] bus_add_driver+0xd6/0x240 [ 1.890567] [] ? pnp_device_detach+0x40/0x40 [ 1.890982] [] driver_register+0x65/0x160 [ 1.891381] [] ? platform_driver_register+0x3b/0x40 [ 1.891877] [] ? early_serial_setup+0xd2/0xd2 [ 1.892295] [] pnp_register_driver+0x17/0x20 [ 1.892724] [] serial8250_pnp_init+0xd/0xf [ 1.893185] [] do_one_initcall+0x112/0x160 [ 1.893605] [] kernel_init+0xf7/0x18e [ 1.893987] [] ? do_early_param+0x7a/0x7a [ 1.894394] [] ? start_kernel+0x324/0x324 [ 1.894818] [] kernel_thread_helper+0x6/0xd Thanks, Fengguang