On Thu, Oct 21, 2021 at 07:00:28PM -0700, Zev Weiss wrote: > Per v0.3 of the Devicetree Specification [0]: > > Indicates that the device is operational, but should not be used. > Typically this is used for devices that are controlled by another > software component, such as platform firmware. > > One use-case for this is in OpenBMC, where certain devices (such as a > BIOS flash chip) may be shared by the host and the BMC, but cannot be > accessed by the BMC during its usual boot-time device probing, because > they require additional (potentially elaborate) coordination with the > host to arbitrate which processor is controlling the device. > > Devices marked with this status should thus be instantiated, but not > have a driver bound to them or be otherwise touched. > > [0] https://github.com/devicetree-org/devicetree-specification/releases/download/v0.3/devicetree-specification-v0.3.pdf > > Signed-off-by: Zev Weiss <zev@xxxxxxxxxxxxxxxxx> > --- > drivers/of/base.c | 56 +++++++++++++++++++++++++++++++++++++++------- > include/linux/of.h | 6 +++++ > 2 files changed, 54 insertions(+), 8 deletions(-) > > diff --git a/drivers/of/base.c b/drivers/of/base.c > index 0ac17256258d..3bd7c5b8a2cc 100644 > --- a/drivers/of/base.c > +++ b/drivers/of/base.c > @@ -580,14 +580,16 @@ int of_machine_is_compatible(const char *compat) > EXPORT_SYMBOL(of_machine_is_compatible); > > /** > - * __of_device_is_available - check if a device is available for use > + * __of_device_check_status - check if a device's status matches a particular string > * > - * @device: Node to check for availability, with locks already held > + * @device: Node to check status of, with locks already held > + * @val: Status string to check for, or NULL for "okay"/"ok" > * > - * Return: True if the status property is absent or set to "okay" or "ok", > - * false otherwise > + * Return: True if status property exists and matches @val, or either "okay" > + * or "ok" if @val is NULL, or if status property is absent and @val is > + * "okay", "ok", or NULL. False otherwise. > */ > -static bool __of_device_is_available(const struct device_node *device) > +static bool __of_device_check_status(const struct device_node *device, const char *val) > { > const char *status; > int statlen; > @@ -596,17 +598,35 @@ static bool __of_device_is_available(const struct device_node *device) > return false; > > status = __of_get_property(device, "status", &statlen); > - if (status == NULL) > - return true; > + if (!status) { > + /* a missing status property is treated as "okay" */ > + status = "okay"; > + statlen = strlen(status) + 1; /* property lengths include the NUL terminator */ > + } > > if (statlen > 0) { > - if (!strcmp(status, "okay") || !strcmp(status, "ok")) > + if (!val && (!strcmp(status, "okay") || !strcmp(status, "ok"))) > + return true; > + else if (val && !strcmp(status, val)) Ick, where is this string coming from? The kernel or userspace or a device tree? This feels very wrong, why is the kernel doing parsing like this of different options that all mean the same thing? > return true; > } > > return false; > } > > +/** > + * __of_device_is_available - check if a device is available for use > + * > + * @device: Node to check for availability, with locks already held > + * > + * Return: True if the status property is absent or set to "okay" or "ok", > + * false otherwise > + */ > +static bool __of_device_is_available(const struct device_node *device) > +{ > + return __of_device_check_status(device, NULL); > +} > + > /** > * of_device_is_available - check if a device is available for use > * > @@ -628,6 +648,26 @@ bool of_device_is_available(const struct device_node *device) > } > EXPORT_SYMBOL(of_device_is_available); > > +/** > + * of_device_is_reserved - check if a device is marked as reserved > + * > + * @device: Node to check for reservation > + * > + * Return: True if the status property is set to "reserved", false otherwise > + */ > +bool of_device_is_reserved(const struct device_node *device) > +{ > + unsigned long flags; > + bool res; > + > + raw_spin_lock_irqsave(&devtree_lock, flags); > + res = __of_device_check_status(device, "reserved"); > + raw_spin_unlock_irqrestore(&devtree_lock, flags); Why is this a "raw" spinlock? Where is this status coming from? > + > + return res; > +} > +EXPORT_SYMBOL(of_device_is_reserved); EXPORT_SYMBOL_GPL()? thanks, greg k-h
