On Tuesday, January 22, 2013 05:03:59 PM Greg Kroah-Hartman wrote: > On Wed, Jan 23, 2013 at 01:17:47AM +0100, Rafael J. Wysocki wrote: > > On Wednesday, January 23, 2013 01:08:54 AM Rafael J. Wysocki wrote: > > > On Tuesday, January 22, 2013 03:56:24 PM Greg Kroah-Hartman wrote: > > > > On Tue, Jan 22, 2013 at 03:28:23AM +0100, Rafael J. Wysocki wrote: > > > > [...] > > > > > > Oh, and same question about racing userspace, you will have problems > > > > here in that the symlinks will be showing up after the device is > > > > created. Perhaps, to make the whole thing easier, you just change the > > > > acpi core code to hold off on the notification until you get all of > > > > these links and files set up and then tell userspace. That's probably > > > > an easier fix. > > > > > > I suppose so. > > > > > > How can I do that? > > > > Should I set dev->kobj.uevent_suppress before calling device_register() and > > then clear it and call the kobject_uevent(&dev->kobj, KOBJ_ADD) from the ACPI > > core after device_register() has returned and the files have been created? > > Ick, that might work, but the "traditional" way is to just do the > creation of the device in two steps. > > First call device_initialize(). Then you can do what you want to the > device, add sysfs files, etc. Then call device_add() which "finalizes" > the device in the driver core and tells userspace all about it. Well, this quite obviously doesn't work. :-) If I call acpi_device_setup_files() between device_initialize() and device_add(), it will trigger the BUG_ON() in sysfs_create_file(), because kobj->sd is still NULL at this point. > The USB core has been doing this since the beginning of time (well, since we > wrote the driver model) and it has worked out pretty well. I guess it does something slightly different from what I need to do, however. > Calling dev_set_uevent_suppress() would also probably work, like you > point out the firmware core uses this. I think I'll need to use this approach. I think that it still will be prudent to call device_initialize() before dev_set_uevent_suppress(), though. I'll post a new series including this later today. > Hm, it uses this to create some sysfs files and then tell userspace about > them, even though it uses device_add(), that's "odd". Well, it seems to have the same problem as I do (described above). > Either way should be fine, you can run 'udevadm monitor' as root to > watch the sysfs events be sent from the kernel to make sure you have it > all working properly. Unfortunately, core ACPI device objects are created way too early for user space to be useful and I don't have any systems with ACPI-based hotplug around here ... Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
