linux-kernel - Re: [PATCH 2/2] speakup: only build serialio when ISA is enabled

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Date:   Tue, 4 Aug 2020 17:35:42 +0200
From:   Samuel Thibault <samuel.thibault@...-lyon.org>
To:     Greg KH <gregkh@...uxfoundation.org>,
        linux-riscv@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        speakup@...ux-speakup.org
Subject: Re: [PATCH 2/2] speakup: only build serialio when ISA is enabled

Greg KH, le mar. 04 août 2020 13:58:17 +0200, a ecrit:
> 	ERROR: modpost: "spk_serial_io_ops" [drivers/accessibility/speakup/speakup_keypc.ko] undefined!
> 	ERROR: modpost: "spk_stop_serial_interrupt" [drivers/accessibility/speakup/speakup_keypc.ko] undefined!

Oh, indeed, these are not covered by the first patch.

I realize that KEYPC depends on ISA, but with COMPILE_TEST as
alternative. We can build serialio in the COMPILE_TEST case too, I'll
update the patches.

But then we'll still have:

> the riscv build issues.

Actually I was surprised by the riscv build issue: the issue is within
riscv's inb() implementation, serialio.c is only calling it.
arch/riscv/include/asm/io.h says:

#define PCI_IOBASE		((void __iomem *)PCI_IO_START)
[...]
#define inb(c)		({ u8  __v; __io_pbr(); __v = readb_cpu((void*)(PCI_IOBASE + (c))); __io_par(__v); __v; })

and thus yes it's arithmetic over a (void*) pointer, the caller cannot
do anything about it.

8250_port.c itself uses inb(), doesn't it get a warning as well? Or is
it getting compiled-out on riscv because of some Kconfig condition?  I
see that the whole drivers/tty/serial is under HAS_IOMEM, and that's the
only condition I can see for 8250_port.c (except SERIAL_8250 of course),
is that it, or is SERIAL_8250 just not enabled in the riscv bot?

Actually the warning seems new, when looking at the Debian build log:

https://buildd.debian.org/status/fetch.php?pkg=linux&arch=riscv64&ver=5.7.10-1&stamp=1595803499&raw=0

and looking for serialio.c, I do not see a warning, and its code hasn't
changed. Is the build bot compiler just more talkative?

Samuel