Re: [PATCH 6/8] i3c: master: Defer new-device registration out of DAA caller context
Adrian Hunter <[email protected]>
| Newsgroups | org.infradead.lists.linux-i3c,org.kernel.vger.linux-kernel |
|---|---|
| Organization | Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki |
| Message-ID | <[email protected]> |
On 12/05/2026 19:39, Frank Li wrote: > On Tue, May 12, 2026 at 03:17:30PM +0300, Adrian Hunter wrote: >> Master drivers may invoke i3c_master_do_daa_ext() during resume to >> re-run Dynamic Address Assignment. As well as assigning addresses to >> any newly arrived devices, this restores the dynamic address of devices >> that lost it across system suspend, so it has to run as part of the >> controller's resume path. >> >> A side effect of i3c_master_do_daa_ext() today is that it also >> registers any newly discovered I3C devices with the driver model >> inline, via i3c_master_register_new_i3c_devs(). Doing that from the >> resume path is problematic: a hot-join-capable device may join the bus >> during this same DAA, and registering it immediately would push driver >> model work (probing, sysfs, etc.) into the controller's resume context, >> where the rest of the system is not yet fully resumed and the >> controller driver is still partway through its own resume sequence. >> >> Decouple discovery from registration: add a reg_work work item to >> struct i3c_master_controller and have i3c_master_do_daa_ext() queue it >> on master->wq (the freezable workqueue) instead of calling >> i3c_master_register_new_i3c_devs() directly. The worker performs the >> registration only when the controller is not shutting_down, and is >> cancelled alongside hj_work in i3c_master_shutdown(). Because wq is >> freezable, any newly observed devices end up being registered after >> the system has finished resuming. >> >> i3c_master_register() also routes its initial post-bus-init registration >> through reg_work, using flush_work() to keep probe-time behavior >> synchronous. This keeps a single registration code path and ensures the >> worker is the only writer of desc->dev. > > why not direct use hj_work? i3c_master_register_new_i3c_devs() use of desc->dev is racy, so i3c_master_register_new_i3c_devs() must not be allowed to race with itself. Having it only ever run via reg_work achieves that. -- linux-i3c mailing list [email protected] http://lists.infradead.org/mailman/listinfo/linux-i3c