| Message ID | 1441628627-5143-21-git-send-email-tomeu.vizoso@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Sep 07, 2015 at 02:23:45PM +0200, Tomeu Vizoso wrote: > Add a field to struct device that instructs the device-driver core to > defer the probe of this device until the late_initcall level. > > By letting all built-in drivers to register before starting to probe, we > can avoid any deferred probes by probing dependencies on demand. Is this not going to resut in massive churn as we go through and set this flag for a massive proportion of drivers? Could we mitigate this by having a first pass at setting this per subsystem or something so that we get a good proportion of drivers with changes in core code?
On 11 September 2015 at 14:17, Mark Brown <broonie@kernel.org> wrote: > On Mon, Sep 07, 2015 at 02:23:45PM +0200, Tomeu Vizoso wrote: >> Add a field to struct device that instructs the device-driver core to >> defer the probe of this device until the late_initcall level. >> >> By letting all built-in drivers to register before starting to probe, we >> can avoid any deferred probes by probing dependencies on demand. > > Is this not going to resut in massive churn as we go through and set > this flag for a massive proportion of drivers? Could we mitigate this > by having a first pass at setting this per subsystem or something so > that we get a good proportion of drivers with changes in core code? I think this flag should be only set during the initial registration of devices (eg. acpi_device_add, of_device_add, etc), as by delaying the probe of those we are automatically delaying the probe of the rest. Regards, Tomeu
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 98504ec99c7d..44b5d33b1f49 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -324,4 +324,22 @@ config CMA_ALIGNMENT endif +config DELAY_DEVICE_PROBES + bool "Allow delaying the probe of some devices" + default y + help + Devices can be matched to a driver and probed from the moment they + are registered, but early during boot their probes are likely to be + deferred because some dependency isn't available yet because most + drivers haven't been registered yet. + + Enabling this option allows the device registration code to delay the + probing of a specific device until device_initcall_sync, when all + built-in drivers have been registered already. + + In some platforms there may be implicit assumptions about when some + devices are probed, so enabling this option could cause problems there. + + If unsure, say Y here. + endmenu diff --git a/drivers/base/dd.c b/drivers/base/dd.c index faf60bfc46b3..0654fb771a53 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -417,6 +417,13 @@ int driver_probe_device(struct device_driver *drv, struct device *dev) if (!device_is_registered(dev)) return -ENODEV; +#if IS_ENABLED(CONFIG_DELAY_DEVICE_PROBES) + if (!driver_deferred_probe_enable && dev->probe_late) { + driver_deferred_probe_add(dev); + return 0; + } +#endif + pr_debug("bus: '%s': %s: matched device %s with driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name); diff --git a/include/linux/device.h b/include/linux/device.h index d8be07bc9c3f..fe5c50ffd7d3 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -748,6 +748,7 @@ struct device_dma_parameters { * * @offline_disabled: If set, the device is permanently online. * @offline: Set after successful invocation of bus type's .offline(). + * @probe_late: If set, device will be probed in the late initcall level. * * At the lowest level, every device in a Linux system is represented by an * instance of struct device. The device structure contains the information @@ -832,6 +833,7 @@ struct device { bool offline_disabled:1; bool offline:1; + bool probe_late:1; }; static inline struct device *kobj_to_dev(struct kobject *kobj)
Add a field to struct device that instructs the device-driver core to defer the probe of this device until the late_initcall level. By letting all built-in drivers to register before starting to probe, we can avoid any deferred probes by probing dependencies on demand. Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> --- Changes in v4: - Add Kconfig DELAY_DEVICE_PROBES to allow disabling delayed probing in machines with initcalls that depend on devices probing at a given time. Changes in v3: None Changes in v2: None drivers/base/Kconfig | 18 ++++++++++++++++++ drivers/base/dd.c | 7 +++++++ include/linux/device.h | 2 ++ 3 files changed, 27 insertions(+)