[GitHub] [mynewt-core] ccollins476ad opened a new pull request #2073: sys/flash_map: Keep non-overlapping default areas

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ccollins476ad opened a new pull request #2073: sys/flash_map: Keep non-overlapping default areas
URL: https://github.com/apache/mynewt-core/pull/2073
 
 
   Prior to this PR, a device with a flash map in its manufacturing meta region (MMR) would completely ignore the default flash map hardcoded in a firmware image.  The rationale was that changes to the default flash map should not cause devices in the field to lose data present in the affected flash areas.
   
   This is reasonable, but there is one issue - if we add new flash areas to unused portions of flash, devices in the field will not be able to use them since they would not be present in the devices' flash maps.
   
   This PR allows a device to use new flash areas hardcoded in the image.  The device will incorporate such a flash area into its flash map if it meets both of these criteria:
   
   1. The area has a unique ID
   2. The area does not overlap with any other flash areas in the MMR flash map.
   
   The first criterion means that if a firmware image rearranges or resizes some existing flash areas, these changes will *not* be incorporated into the device's flash map.  These areas are not new, they are just modified, so their IDs are already present in the device's MMR flash map.
   
   The second criterion means that the device will only incorporate a new flash area into its flash map if the area resides entirely in unused flash.  If the area overlaps any other areas, it is ignored.  
   

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