On Thu, Jul 1, 2021 at 10:41 AM Geert Uytterhoeven [off-list ref] wrote:

On Wed, Jun 30, 2021 at 9:36 PM John Paul Adrian Glaubitz [off-list ref] wrote:

quoted

On 6/30/21 9:33 PM, Randy Dunlap wrote:

quoted

On 6/30/21 2:36 AM, John Paul Adrian Glaubitz wrote:

quoted

FWIW, there are some warnings when building the SH-7785LCR configuration:

In file included from ./arch/sh/include/asm/hw_irq.h:6,
                 from ./include/linux/irq.h:591,
                 from ./include/asm-generic/hardirq.h:17,
                 from ./arch/sh/include/asm/hardirq.h:9,
                 from ./include/linux/hardirq.h:11,
                 from ./include/linux/interrupt.h:11,
                 from ./include/linux/serial_core.h:13,
                 from ./include/linux/serial_sci.h:6,
                 from arch/sh/kernel/cpu/sh4a/setup-sh7785.c:10:
./include/linux/sh_intc.h:100:63: warning: division 'sizeof (void *) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div]
  100 | #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
      |                                                               ^
./include/linux/sh_intc.h:107:9: note: in expansion of macro '_INTC_ARRAY'
  107 |         _INTC_ARRAY(sense_regs), _INTC_ARRAY(ack_regs), \
      |         ^~~~~~~~~~~
./include/linux/sh_intc.h:124:15: note: in expansion of macro 'INTC_HW_DESC'
  124 |         .hw = INTC_HW_DESC(vectors, groups, mask_regs,                  \
      |               ^~~~~~~~~~~~
arch/sh/kernel/cpu/sh4a/setup-sh7785.c:478:8: note: in expansion of macro 'DECLARE_INTC_DESC'
  478 | static DECLARE_INTC_DESC(intc_desc, "sh7785", vectors, groups,
      |        ^~~~~~~~~~~~~~~~~

A while ago, I had a look into fixing them, but it was non-trivial.
The issue is that the macros are sometimes used with NULL pointer arrays.
The __same_type() check in

    #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)

is supposed to catch that, but modern compilers seem to evaluate the
non-taken branch, too, leading to the warning.

Anyone with a suggestion? (CCing the multi-compiler guru)

I think I looked at this (or maybe a related sh driver) in the past
and also gave up.

The best idea I have would be to manually expand the DECLARE_INTC_DESC()
macros. It would be possible to add further variations of them for each
combination of NULL/non-NULL arguments, but IMHO they don't actually
add any readability over the expanded version in the first place.

Another option would be to change the definition from array/size to
zero-terminated
arrays and get rid of the sizeof hack.

      Arnd