Le Thu, 5 May 2022 14:37:15 -0500, Rob Herring <robh@xxxxxxxxxx> a écrit : > > + > > +/** > > + * of_property_alloc - Allocate a property dynamically. > > + * @name: Name of the new property > > + * @value: Value that will be copied into the new property value > > + * @value_len: length of @value to be copied into the new property value > > + * @len: Length of new property value, must be greater than @value_len > > What's the usecase for the lengths being different? That doesn't seem > like a common case, so perhaps handle it with a NULL value and > non-zero length. Then the caller has to deal with populating > prop->value. That was actually something used by powerpc code but agreed, letting the user recopy it's values seems fine to me and the usage will be more clear. > > /* > > - * NOTE: There is no check for zero length value. > > - * In case of a boolean property, this will allocate a value > > - * of zero bytes. We do this to work around the use > > - * of of_get_property() calls on boolean values. > > + * Even if the property has no value, it must be set to a > > + * non-null value since of_get_property() is used to check > > + * some values that might or not have a values (ranges for > > + * instance). Moreover, when the node is released, prop->value > > + * is kfreed so the memory must come from kmalloc. > > Allowing for NULL value didn't turn out well... > > We know that we can do the kfree because OF_DYNAMIC is set IIRC... > > If we do 1 allocation for prop and value, then we can test > for "prop->value == prop + 1" to determine if we need to free or not. Sounds like a good idea. -- Clément Léger, Embedded Linux and Kernel engineer at Bootlin https://bootlin.com
