linux-kernel - Question about using #ifdef CONFIG

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Message-ID: <CAFCwf13AtwkWQ4Gnxi6pfKbcdEK95+X__7cFboN1FdHd1aKNQw@mail.gmail.com>
Date:   Sun, 6 Oct 2019 12:33:31 +0300
From:   Oded Gabbay <oded.gabbay@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Question about using #ifdef CONFIG_PPC64 in driver code

Hi Greg,
a while ago we had an argument about identifying in my driver's code
whether I'm running on x86 or powerpc. I tried to do something
dynamically (based on parent pci bridge ID), and you and other people
objected to it.

I see in other drivers (more then a few) that they are using #ifdef
CONFIG_PPC64 in some places for similar things (e.g. to run code that
is only needed in case of powerpc).

e.g. from ocxl driver in misc:

#ifdef CONFIG_PPC64
static long afu_ioctl_enable_p9_wait(struct ocxl_context *ctx,
...
#endif
and also:

#ifdef CONFIG_PPC64
if (cpu_has_feature(CPU_FTR_P9_TIDR))
arg.flags[0] |= OCXL_IOCTL_FEATURES_FLAGS0_P9_WAIT;
#endif

Is this approach acceptable on you ?
Can I do something similar in my driver:

#ifdef CONFIG_PPC64
      foo (64)
#else
      foo (48)
#endif

Thanks,
Oded