On Sun, 2024-02-25 at 11:54 -0500, Jamal Hadi Salim wrote: > Introduce abstraction that represents P4 data types. > This also introduces the Kconfig and Makefile which later patches use. > Numeric types could be little, host or big endian definitions. The abstraction > also supports defining: > > a) bitstrings using P4 annotations that look like "bit<X>" where X > is the number of bits defined in a type > > b) bitslices such that one can define in P4 as bit<8>[0-3] and > bit<16>[4-9]. A 4-bit slice from bits 0-3 and a 6-bit slice from bits > 4-9 respectively. > > c) speacialized types like dev (which stands for a netdev), key, etc > > Each type has a bitsize, a name (for debugging purposes), an ID and > methods/ops. The P4 types will be used by externs, dynamic actions, packet > headers and other parts of P4TC. > > Each type has four ops: > > - validate_p4t: Which validates if a given value of a specific type > meets valid boundary conditions. > > - create_bitops: Which, given a bitsize, bitstart and bitend allocates and > returns a mask and a shift value. For example, if we have type > bit<8>[3-3] meaning bitstart = 3 and bitend = 3, we'll create a mask > which would only give us the fourth bit of a bit8 value, that is, 0x08. > Since we are interested in the fourth bit, the bit shift value will be 3. > This is also useful if an "irregular" bitsize is used, for example, > bit24. In that case bitstart = 0 and bitend = 23. Shift will be 0 and > the mask will be 0xFFFFFF00 if the machine is big endian. > > - host_read : Which reads the value of a given type and transforms it to > host order (if needed) > > - host_write : Which writes a provided host order value and transforms it > to the type's native order (if needed) The type has a 'print' op, but I can't easily find where such op is used and its role?!? Thanks, Paolo
