On 8/14/19 6:48 AM, Les Newell wrote:
I am working on a hal module that may need a variable amount of memory
depending on it's configuration. Is it acceptable to use malloc in a hal
module? Should I use hal_malloc or is that specifically for pins?
Memory management is different for realtime modules and non-realtime
modules.
Non-realtime modules can do whatever they want, whenever they want.
Realtime modules have to go through two APIs to do memory management:
HAL pins & params must be allocated with the hal_*_new() functions.
Those functions may be called only after a successful call to
hal_init(), and before the call to hal_exit() . hal_exit() also
automatically frees everything allocated with hal_*_new().
Normal (non-HAL) memory must be allocated with the rtapi_kmalloc()
functions. Direct calls to malloc(), kmalloc(), mmap(), etc are not
allowed.
The rtapi memory management functions are (barely) documented in the
(confusingly named) "rtapi_slab" manpage:
http://linuxcnc.org/docs/2.7/html/man/man3/rtapi_slab.3rtapi.html
The rtapi memory management functions may only by called after a
successful call to rtapi_init(), though note that hal_init() calls
rtapi_init() for you. The memory allocated by rtapi_kmalloc() must be
expliticly returned with rtapi_kfree().
--
Sebastian Kuzminsky
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