On Thu, Feb 29, 2024 at 10:09 AM Paolo Abeni <pabeni@xxxxxxxxxx> wrote: > > 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 for catching that. We'll remove it. It was part of an operational debugging patch that was not submitted. cheers, jamal > Thanks, > > Paolo >
