bios_emulator: how LOG_inpb() is supposed to work on non-x86 systems?

[Yuri Zaporozhets]

Hi all,

When trying to compile drivers/bios_emulator for RISC-V, I get a
bunch of the following warnings:

================

In file included from drivers/bios_emulator/besys.c:51:
drivers/bios_emulator/besys.c: In function ‘BE_inb’:
./arch/riscv/include/asm/io.h:18:43: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   18 | #define __arch_getb(a)                  (*(volatile unsigned char *)(a))
      |                                           ^
./arch/riscv/include/asm/io.h:33:41: note: in expansion of macro ‘__arch_getb’
   33 | #define __raw_readb(a)                  __arch_getb(a)
      |                                         ^~~~~~~~~~~
./arch/riscv/include/asm/io.h:209:39: note: in expansion of macro ‘__raw_readb’
  209 | #define inb(p)  ({ unsigned int __v = __raw_readb(__io(p)); __v; })
      |                                       ^~~~~~~~~~~
drivers/bios_emulator/biosemui.h:131:25: note: in expansion of macro ‘inb’
  131 | #define PM_inpb(port)   inb(port)
      |                         ^~~
drivers/bios_emulator/biosemui.h:138:25: note: in expansion of macro ‘PM_inpb’
  138 | #define LOG_inpb(port)  PM_inpb(port)
      |                         ^~~~~~~
drivers/bios_emulator/besys.c:572:31: note: in expansion of macro ‘LOG_inpb’
  572 |                         val = LOG_inpb(port);

================

My question is: how _in principle_ is this supposed to work? On non-x86 systems,
the PCI I/O space must always be accessed using some base address (for example,
for my PCIe video card it's 0x60080000). In the sequence above
(inb -> __raw_readb -> __arch_getb) I do not see such base address at all.
Previously, there was a constant VIDEO_IO_OFFSET added to the port
(see 70f2030f02696ee1820d8df690e878de078b01b3), but it was removed completely.

In arch/riscv/include/asm/io.h, the I/O primitives are defined as:

#define inb(p)  ({ unsigned int __v = __raw_readb(__io(p)); __v; })

where the __io() macro seems to be an excellent thing to account for the
I/O base address. I would expect that the driver that uses PCI I/O
defines something like:

#define __io(port) (base_addr + port)

where base_addr is a runtime variable. But instead both bios.c and besys.c
have just "#define __io", without any parameters.

I am totally puzzled. I would be grateful for any clarification how this code
was supposed to work in the first place.

P.S. Simon, adding you to CC: since you were working on this code in the past.

Thanks in advance.

-- 
Regards,
Yuri