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update sysarch doc. patch #1233
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@ -16,6 +16,11 @@ functionality. Previous versions of lwIP required the sys_arch to
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implement timer scheduling as well but as of lwIP 0.5 this is
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implemented in a higher layer.
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In addition to the source file providing the functionality of sys_arch,
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the OS emulation layer must provide several header files defining
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macros used throughout lwip. The files required and the macros they
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must define are listed below the sys_arch description.
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Semaphores can be either counting or binary - lwIP works with both
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kinds. Mailboxes are used for message passing and can be implemented
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either as a queue which allows multiple messages to be posted to a
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@ -42,13 +47,13 @@ The following functions must be implemented by the sys_arch:
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- void sys_sem_free(sys_sem_t sem)
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Deallocates a semaphore.
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Deallocates a semaphore.
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- void sys_sem_signal(sys_sem_t sem)
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Signals a semaphore.
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- u16_t sys_arch_sem_wait(sys_sem_t sem, u16_t timeout)
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- u32_t sys_arch_sem_wait(sys_sem_t sem, u32_t timeout)
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Blocks the thread while waiting for the semaphore to be
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signaled. If the "timeout" argument is non-zero, the thread should
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@ -82,7 +87,7 @@ The following functions must be implemented by the sys_arch:
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Posts the "msg" to the mailbox.
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- u16_t sys_arch_mbox_fetch(sys_mbox_t mbox, void **msg, u16_t timeout)
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- u32_t sys_arch_mbox_fetch(sys_mbox_t mbox, void **msg, u32_t timeout)
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Blocks the thread until a message arrives in the mailbox, but does
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not block the thread longer than "timeout" milliseconds (similar to
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@ -123,24 +128,71 @@ to be implemented as well:
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- sys_prot_t sys_arch_protect(void)
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This optional function does a "fast" critical region protection and returns
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the previous protection level. This function is only called during very short
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critical regions. An embedded system which supports ISR-based drivers might
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want to implement this function by disabling interrupts. Task-based systems
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might want to implement this by using a mutex or disabling tasking. This
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function should support recursive calls from the same task or interrupt. In
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other words, sys_arch_protect() could be called while already protected. In
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that case the return value indicates that it is already protected.
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This optional function does a "fast" critical region protection and returns
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the previous protection level. This function is only called during very short
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critical regions. An embedded system which supports ISR-based drivers might
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want to implement this function by disabling interrupts. Task-based systems
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might want to implement this by using a mutex or disabling tasking. This
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function should support recursive calls from the same task or interrupt. In
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other words, sys_arch_protect() could be called while already protected. In
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that case the return value indicates that it is already protected.
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sys_arch_protect() is only required if your port is supporting an operating
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system.
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sys_arch_protect() is only required if your port is supporting an operating
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system.
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- void sys_arch_unprotect(sys_prot_t pval)
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This optional function does a "fast" set of critical region protection to the
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value specified by pval. See the documentation for sys_arch_protect() for
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more information. This function is only required if your port is supporting
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an operating system.
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This optional function does a "fast" set of critical region protection to the
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value specified by pval. See the documentation for sys_arch_protect() for
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more information. This function is only required if your port is supporting
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an operating system.
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-------------------------------------------------------------------------------
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Additional files required for the "OS support" emulation layer:
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-------------------------------------------------------------------------------
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cc.h - Architecture environment, some compiler specific, some
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environment specific (probably should move env stuff
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to sys_arch.h.)
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Typedefs for the types used by lwip -
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u8_t, s8_t, u16_t, s16_t, u32_t, s32_t, mem_ptr_t
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Compiler hints for packing lwip's structures -
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PACK_STRUCT_FIELD(x)
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PACK_STRUCT_STRUCT
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PACK_STRUCT_BEGIN
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PACK_STRUCT_END
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Platform specific diagnostic output -
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LWIP_PLATFORM_DIAG(x) - non-fatal, print a message.
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LWIP_PLATFORM_ASSERT(x) - fatal, print message and abandon execution.
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"lightweight" synchronization mechanisms -
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SYS_ARCH_DECL_PROTECT(x) - declare a protection state variable.
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SYS_ARCH_PROTECT(x) - enter protection mode.
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SYS_ARCH_UNPROTECT(x) - leave protection mode.
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If the compiler does not provide memset() this file must include a
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definition of it, or include a file which defines it.
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This file must either include a system-local <errno.h> which defines
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the standard *nix error codes, or it should #define LWIP_PROVIDE_ERRNO
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to make lwip/arch.h define the codes which are used throughout.
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perf.h - Architecture specific performance measurement.
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Measurement calls made throughout lwip, these can be defined to nothing.
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PERF_START - start measuring something.
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PERF_STOP(x) - stop measuring something, and record the result.
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sys_arch.h - Tied to sys_arch.c
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Arch dependent types for the following objects:
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sys_sem_t, sys_mbox_t, sys_thread_t,
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And, optionally:
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sys_prot_t
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Defines to set vars of sys_mbox_t and sys_sem_t to NULL.
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SYS_MBOX_NULL NULL
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SYS_SEM_NULL NULL
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