defxx: DEFEA's ESIC port I/O decoding cleanup

Hello Maciej W. Rozycki,

The patch b98dfaf2b0a3: "defxx: DEFEA's ESIC port I/O decoding cleanup" from Sep 25, 2014, leads to the following static checker warning:

	drivers/net/fddi/defxx.c:741 dfx_bus_init()
	warn: odd binop '0x3 & 0xfffffffffffffffc'

drivers/net/fddi/defxx.c

   729                  val = PI_IO_CMP_M_SLOT;
   730                  outb(val, base_addr + PI_ESIC_K_IO_ADD_MASK_0_1);
   731                  val = (PI_ESIC_K_CSR_IO_LEN - 1) & ~3;
   732                  outb(val, base_addr + PI_ESIC_K_IO_ADD_MASK_0_0);
   733  
   734                  val = 0;
   735                  outb(val, base_addr + PI_ESIC_K_IO_ADD_CMP_1_1);
   736                  val = PI_DEFEA_K_BURST_HOLDOFF;
   737                  outb(val, base_addr + PI_ESIC_K_IO_ADD_CMP_1_0);
   738  
   739                  val = PI_IO_CMP_M_SLOT;
   740                  outb(val, base_addr + PI_ESIC_K_IO_ADD_MASK_1_1);
   741                  val = (PI_ESIC_K_BURST_HOLDOFF_LEN - 1) & ~3;
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is just saying "val = 0" in a complicated way. It's not clear what was intended...

   742                  outb(val, base_addr + PI_ESIC_K_IO_ADD_MASK_1_0);
   743  

regards,
dan carpenter

This is self-documenting code, plus if PI_ESIC_K_BURST_HOLDOFF_LEN is
ever set to something else to what it is now (please be aware this piece of hardware is not fully documented), then there'll be no need to review code throughout to update mask calculation. See a similar calculation for PI_ESIC_K_CSR_IO_LEN and the board's other address decode register above.

In this case the resulting mask comes out as all-zeros, meaning no
address bits will be discarded in decoding, i.e. only a single address will match, which is exactly what is needed here. This is a 32-bit register we don't want partial accesses to and hence the ~3 mask.

I think your checker might be just a little bit too picky for this case,
although I realise this pickiness may catch dumb mistakes elsewhere and save people trouble where a pair of disjoint mask is not really intended unlike here. Thanks for the heads-up therefore, but this code is good and I plan to keep it like this. :)

Maciej

Yeah. This check is too picky for me to release publicly. Often I can tell which uses are intentional but sometimes it's not clear.

Anyway, thanks for the feedback.

regards,
dan carpenter