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

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Message-ID: <27e2909a0bc94177af1afe56da618fba@realtek.com>
Date:   Thu, 5 Jan 2023 00:56:15 +0000
From:   Ping-Ke Shih <pkshih@...ltek.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        David Laight <David.Laight@...lab.com>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "kvalo@...nel.org" <kvalo@...nel.org>,
        "tehuang@...ltek.com" <tehuang@...ltek.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "tony0620emma@...il.com" <tony0620emma@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/4] rtw88: Add packed attribute to the eFuse structs


> -----Original Message-----
> From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> Sent: Thursday, January 5, 2023 1:49 AM
> To: David Laight <David.Laight@...lab.com>
> Cc: Ping-Ke Shih <pkshih@...ltek.com>; linux-wireless@...r.kernel.org; kvalo@...nel.org;
> tehuang@...ltek.com; s.hauer@...gutronix.de; tony0620emma@...il.com; netdev@...r.kernel.org;
> linux-kernel@...r.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@...lab.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