Dear udev developers, We (me and some kernel devs mostly) would like to add support to the kernel for userspace telling the kernel that it is done with the *initial* loading of modules, with the purpose of cleaning up (disabling) unused harware resources like e.g. regulators and clocks. Currently the kernel does this cleanup just before it starts init (which may very well be init from a ramdisk). In some cases this is too early really, because later on a module may get loaded which needs this resources, these resources will then get turned on again by the loaded driver, and most of the time this is not an issue, but sometimes it is. I realize very well that there is no magic moment where udev is really ever done loading modules, but the case which we want to support only involves devices which are *already enumerated*, but may not yet have a driver loaded, when udev starts. We would like udev to emit a signal (ABI to be discussed) when it is done trying to load modules for everything which was already enumerated when it starts, iow when there are no new device events pending anymore when udev does its initial hotplug replay. So the question to you is would you be willing to include such functionality in udev ? Note this signal would need to be emitted when udev from the real rootfs is done with the initial module loading, as the real rootfs may very well have more modules available then the initrd. ### With the generic story above told let me also give the concrete example / problem which has let to me asking this (note this has been brought up before on various kernel lists, it is a re-occuring theme, this is just an example really) : The problem at hand is a sata connector which also has a sata-power connector on an embedded (ish) board where the sata-power is controlled through a gpio. The sata-power connector is modeled in devicetree as a power-supply and this supply gets controlled by the ahci_platform driver. The disk power may very well have already been turned on by the bootloader, so we add a regulator-boot-on property to the regulator node in devicetree to make sure that it is left untouched when the regulator driver loads. If the ahci_platform driver is build into the kernel, it will then take control of the regulator and everything works well. If however the ahci_platform driver is a module, then as soon as the kernel is ready to start init, unused regulators are turned off and the disk looses its power while spinning and ends up doing an emergency heads park. Then as soon as the ahci_platform module loads the disk is spin up again. This is not good (quite bad actually) for the lifetime of the disk. Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
