Re: net: intel/e1000e/netdev.c __ew32_prepare parameter not used?

On Tue, Aug 3, 2021 at 5:50 AM Michael Walle [off-list ref] wrote:

Hi,

quoted

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.