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kernel/device: add arg checking in z_device_ready()

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If this call receives an invalid device pointer as argument it
assumes that the `device` is not ready for usage.

This routine is currently called by two device specific APIs:

    - device_usable_check(const struct device *dev)
    - device_is_ready(const struct device *dev)

The device-specific APIs documentation claims that these two
routines must be called with a device pointer captured from
DEVICE_DT_GET(). So passing NULL is a violation of the rule.

Nevertheless, is quite common in drivers to assign NULL to
a device pointer if the corresponding DT property has not been
found (e.g. a not used gpio interrupt declaration for a given
device instance) and seems legit to interpret this condition
same as the device is not ready for usage.

Signed-off-by: Armando Visconti <armando.visconti@st.com>
This commit is contained in:
Armando Visconti 2021-05-13 18:24:25 +02:00 • committed by Kumar Gala
commit 4b4068c948
2 changed files with 12 additions and 3 deletions
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7
include/device.h
View file

@ -581,8 +581,8 @@ static inline int z_device_usable_check(const struct device *dev)
* distinct error values that identify the reason if it cannot. * distinct error values that identify the reason if it cannot.
* *
* @retval 0 if the device is usable. * @retval 0 if the device is usable.
* @retval -ENODEV if the device has not been initialized, or the * @retval -ENODEV if the device has not been initialized, the device pointer
* initialization failed. * is NULL or the initialization failed.
* @retval other negative error codes to indicate additional conditions that * @retval other negative error codes to indicate additional conditions that
* make the device unusable. * make the device unusable.
*/ */
@ -606,7 +606,8 @@ static inline int z_impl_device_usable_check(const struct device *dev)
* @param dev pointer to the device in question. * @param dev pointer to the device in question.
* *
* @retval true if the device is ready for use. * @retval true if the device is ready for use.
* @retval false if the device is not ready for use. * @retval false if the device is not ready for use or if a NULL device pointer
* is passed as argument.
*/ */
static inline bool device_is_ready(const struct device *dev) static inline bool device_is_ready(const struct device *dev)
{ {

8
kernel/device.c
View file

@ -163,6 +163,14 @@ size_t z_device_get_all_static(struct device const **devices)
bool z_device_ready(const struct device *dev) bool z_device_ready(const struct device *dev)
{ {
/*
* if an invalid device pointer is passed as argument, this call
* reports the `device` as not ready for usage.
*/
if (dev == NULL) {
return false;
}
return dev->state->initialized && (dev->state->init_res == 0U); return dev->state->initialized && (dev->state->init_res == 0U);
} }