RTEMS Porting Guide
The _CPU_Priority_bits_index routine translates the bit numbers
returned by _CPU_Bitfield_Find_first_bit() into something
suitable for use as a major or minor component of a priority.
The find first bit routine may number the bits in a
way that is difficult to map into the major and minor components
of the priority. For example, when finding the first bit set in
the value 0x8000, a CPU may indicate that bit 15 or 16 is set
based on whether the least significant bit is "zero" or "one".
Similarly, a CPU may only scan 32-bit values and consider the
most significant bit to be bit zero or one. In this case, this
would be bit 16 or 17.
This routine allows that unwieldy form to be converted into a normalized form that is easier to process and use as an index.
#if (CPU_USE_GENERIC_BITFIELD_CODE == FALSE) #define _CPU_Priority_bits_index( _priority ) \ (_priority) #endif
RTEMS Porting Guide
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