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# Software Memory RTOS Driver

This driver allows for implementing application defined software memory in an RTOS.

bool rtos_swmem_read_request_isr(unsigned offset, uint32_t *buf)

  Services a software memory read request from within the software memory fill interrupt handler. This function may be provided by the application when the software memory driver is initialized with the RTOS_SWMEM_READ_FLAG flag. If the application code to satisfy a fill request requires being run from within an RTOS thread, then rtos_swmem_read_request() should be used instead. Both this handler and rtos_swmem_read_request() may be used together. If the ISR handler is able to satisfy the request it should return true. If it is not, but the request can be satisfied from within rtos_swmem_read_request(), then it should return false.

  Parameters:

    - offset – The byte offset into the software memory of the cache line that has had a cache miss.

    - buf – This function must fill this with SWMEM_EVICT_SIZE_WORDS words of data. Where this data comes from is up to the application. One example is from a flash memory.

  Return values:

    - true – if the fill request was satisfied.

    - false – if the fill request was not satisfied. This requires that rtos_swmem_read_request() also be provided.

bool rtos_swmem_write_request_isr(unsigned offset, uint32_t dirty_mask, const uint32_t *buf)

  Services a software memory write request from within the software memory fill interrupt handler. This function may be provided by the application when the software memory driver is initialized with the RTOS_SWMEM_WRITE_FLAG flag. If the application code to satisfy an evict request requires being run from within an RTOS thread, then rtos_swmem_write_request() should be used instead. Both this handler and rtos_swmem_write_request() may be used together. If the ISR handler is able to satisfy the request it should return true. If it is not, but the request can be satisfied from within rtos_swmem_write_request(), then it should return false.

  Parameters:

    - offset – The byte offset into the software memory of the cache line that is being evicted.

    - dirty_mask – A bytewise dirty mask for the data in `buf`. The least significant bit corresponds to the lowest byte address in `buf` and each subsequent byte address corresponds to the next least significant bit.

    - buf – A pointer to a buffer containing SWMEM_EVICT_SIZE_WORDS words of data from the cache line being evicted. It is up to the application what it does with this data. One example is to write it to flash memory.

  Return values:

    - true – if the evict request was satisifed.

    - false – if the evict request was not satisfied. This requires that rtos_swmem_write_request() also be provided.

void rtos_swmem_read_request(unsigned offset, uint32_t *buf)

  Services a software memory read request from within the software memory RTOS thread. This function may be provided by the application when the software memory driver is initialized with the RTOS_SWMEM_READ_FLAG flag. If rtos_swmem_read_request_isr() is also implemented, then it will be called first. If it is unable to satisfy the request, then this handler will be called. See the description for rtos_swmem_read_request_isr().

  Parameters:

    - offset – The byte offset into the software memory of the cache line that has had a cache miss.

    - buf – This function must fill this with SWMEM_EVICT_SIZE_WORDS words of data. Where this data comes from is up to the application. One example is from a flash memory.

void rtos_swmem_write_request(unsigned offset, uint32_t dirty_mask, const uint32_t *buf)

  Services a software memory write request from within the software memory RTOS thread. This function may be provided by the application when the software memory driver is initialized with the RTOS_SWMEM_WRITE_FLAG flag. If rtos_swmem_write_request_isr() is also implemented, then it will be called first. If it is unable to satisfy the request, then this handler will be called. See the description for rtos_swmem_write_request_isr().

  Parameters:

    - offset – The byte offset into the software memory of the cache line that is being evicted.

    - dirty_mask – A bytewise dirty mask for the data in `buf`. The least significant bit corresponds to the lowest byte address in `buf` and each subsequent byte address corresponds to the next least significant bit.

    - buf – A pointer to a buffer containing SWMEM_EVICT_SIZE_WORDS words of data from the cache line being evicted. It is up to the application what it does with this data. One example is to write it to flash memory.

void rtos_swmem_start(unsigned priority)

  Starts the RTOS software memory driver.

  Parameters:

    - priority – The priority of the task that gets created by the driver to service the software memory.

void rtos_swmem_init(uint32_t init_flags)

  Initializes the software memory for use by the RTOS software memory driver.

  Parameters:

    - init_flags – A bitfield consisting of initialization flags.

      - RTOS_SWMEM_READ_FLAG enables swmem reads.

      - RTOS_SWMEM_WRITE_FLAG enables swmem writes.

unsigned int rtos_swmem_offset_get()

  Return the offset from XS1_SWMEM_BASE to the start of the software memory.

RTOS_SWMEM_READ_FLAG

  Flag indicating that software memory reads should be enabled. This should probably always be set when using software memory.

RTOS_SWMEM_WRITE_FLAG

  Flag indicating that software memory writes should be enabled. This will not always need to be set, especially if flash is backing the software memory and intended to be read only.