diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/porting-guide.rst | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/docs/porting-guide.rst b/docs/porting-guide.rst index 83fac2860..84f4c9dfa 100644 --- a/docs/porting-guide.rst +++ b/docs/porting-guide.rst @@ -1075,21 +1075,22 @@ Function : plat\_get\_mbedtls\_heap() :: Arguments : void **heap_addr, size_t *heap_size - Return : int + Return : int This function is invoked during Mbed TLS library initialisation to get a heap, by means of a starting address and a size. This heap will then be used -internally by the Mbed TLS library. The heap is requested from the current -BL stage, i.e. the current BL image inside which Mbed TLS is used. - -The default implementation allocates a new heap every time Mbed TLS gets -initialised. This means that a new heap is statically allocated inside -every image (i.e. every BL stage) that utilises Mbed TLS. In the default -implementation, this function returns the address and size of this default -heap. However, by overriding the default implementation, platforms have the ability -to optimise memory usage. - -On success it returns 0 and a negative error code otherwise. +internally by the Mbed TLS library. The heap is requested from the current BL +stage, i.e. the current BL image inside which Mbed TLS is used. + +In the default implementation a heap is statically allocated inside every image +(i.e. every BL stage) that utilises Mbed TLS. So, in this case, the function +simply returns the address and size of this "pre-allocated" heap. However, by +overriding the default implementation, platforms have the potential to optimise +memory usage. For example, on some Arm platforms, the Mbed TLS heap is shared +between BL1 and BL2 stages and, thus, the necessary space is not reserved +twice. + +On success the function should return 0 and a negative error code otherwise. Modifications specific to a Boot Loader stage --------------------------------------------- |