linux-kernel - RE: [PATCH 4/5] platform/x86/intel/ifs: Implement Array BIST test

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Date:   Wed, 1 Feb 2023 19:43:23 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Hansen, Dave" <dave.hansen@...el.com>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "markgross@...nel.org" <markgross@...nel.org>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Macieira, Thiago" <thiago.macieira@...el.com>,
        "Jimenez Gonzalez, Athenas" <athenas.jimenez.gonzalez@...el.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>
Subject: RE: [PATCH 4/5] platform/x86/intel/ifs: Implement Array BIST test

> Why bother with a bitfield?  Just do:

How much "bother" is a bitfield?

> union ifs_array {
>	u64	data;
>	struct {
>		u32	array_bitmask;
>		u16	array_bank;
>		u16	flags;
>	};
>};
>
> Then you only need to mask 'ctrl_result' out of flags.  You don't need
> any crazy macros.

"only need" to special case this one field ... but that's extra
code for humans to read (and humans aren't good at that)
rather than the computer (compiler) which is really good at
doing this.

Using bitfields is also following the existing style of this driver.

-Tony