RE: [PATCH 1/4] rtw88: Add packed attribute to the eFuse structs

[Ping-Ke Shih <pkshih@realtek.com>]

> -----Original Message-----
> From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Sent: Thursday, January 5, 2023 1:49 AM
> To: David Laight <David.Laight@aculab.com>
> Cc: Ping-Ke Shih <pkshih@realtek.com>; linux-wireless@vger.kernel.org; kvalo@kernel.org;
> tehuang@realtek.com; s.hauer@pengutronix.de; tony0620emma@gmail.com; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 1/4] rtw88: Add packed attribute to the eFuse structs
> 
> On Wed, Jan 4, 2023 at 5:31 PM David Laight <David.Laight@aculab.com> wrote:
> [...]
> > > > What you may want to do is add compile-time asserts for the
> > > > sizes of the structures.
> > > Do I get you right that something like:
> > >   BUILD_BUG_ON(sizeof(rtw8821c_efuse) != 256);
> > > is what you have in mind?
> >
> > That looks like the one...
> I tried this (see the attached patch - it's just meant to show what I
> did, it's not meant to be applied upstream).
> With the attached patch but no other patches this makes the rtw88
> driver compile fine on 6.2-rc2.

I prefer to use static_assert() below the struct if we really need it.
In fact, we only list fields of efuse map we need in the struct, not
full map. 

> 
> Adding __packed to struct rtw8723d_efuse changes the size of that
> struct for me (I'm compiling for AArch64 / ARM64).
> With the packed attribute it has 267 bytes, without 268 bytes.

Try 

static_assert(offsetof(struct rtw8723d_efuse, rf_antenna_option) == 0xc9);

and other fields to bisect which field gets wrong.

Ping-Ke