It's better to save one argument by returning pid directly.
This change also follow the convention of task_create.
BTW, it is reasonable to adjust the function prototype a
little bit from both implementation and consistency since
task_spawn is NuttX specific API.
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
task_spawn() and posix_spawn() are NuttX OS interfaces. In PROTECTED and KERNEL build modes, then can be reached from applications only via a system call. Currently, the number of parameters in a system call is limited to six; these spawn function have seven parameters. Rather than extend the maximum number of parameters across all architectures, I opted instead to marshal the seven parameters into a structure.
*
In order to support builtin in function in protected mode, a task_spawn() system call must be supported. Unfortunately this is overly complex because there is a (soft) limit of 6 parameters in a system call; task_spawn has seven paramters. This is a soft limit but still difficult to extend because it involves assembly language changes to numerous architectures. Better to get more creative.
