netdev - Re: net: intel/e1000e/netdev.c __ew32

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Message-ID: <CAN6UTawJCj0O-oXSwGoVxjii9JTJ484UKXZzYnqPW1L7JB=jJA@mail.gmail.com>
Date:   Tue, 3 Aug 2021 10:15:44 -0300
From:   Leandro Coutinho <lescoutinhovr@...il.com>
To:     Michael Walle <michael@...le.cc>
Cc:     netdev@...r.kernel.org
Subject: Re: net: intel/e1000e/netdev.c __ew32_prepare parameter not used?

On Tue, Aug 3, 2021 at 5:50 AM Michael Walle <michael@...le.cc> wrote:
>
> Hi,
>
> > It seems the parameter `*hw` is not used.
> > Although I didn't find where `FWSM` is defined.
> >
> > Should it be removed? Or is the parameter really needed?
> >
> > static void __ew32_prepare(struct e1000_hw *hw)
> > {
> >     s32 i = E1000_ICH_FWSM_PCIM2PCI_COUNT;
> >
> >     while ((er32(FWSM) & E1000_ICH_FWSM_PCIM2PCI) && --i)
> >         udelay(50);
> > }
>
> If you have a look at the definition of er32() (which is a macro and
> is defined in e1000.h, you'll see that the hw parameter is used
> there without being a parameter of the macro itself. Thus if you'd
> rename the parameter you'd get a build error.Not really the best
> code to look at when you want to learn coding, because that's an
> example how not to do things, IMHO.
>
> -michael

Thank you very much Michael! =)

er32 is defined as:
#define er32(reg)   __er32(hw, E1000_##reg)

That's why I didn't find any definition for `FWSM` ... because of the
token concatenation https://gcc.gnu.org/onlinedocs/cpp/Concatenation.html

I think this way it would be more clear:
#define er32(hw, reg)   __er32(hw, reg)

I don't know if they did it that way just to avoid typing, or if there is some
other reason.

That is one advantage of Rust: macros have an ! at the end, eg: println!
So you can easily distinguish macros from functions.