linux-kernel - Re: [PATCH net-next 2/2] net: lan966x: Stop using packing library

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Message-ID: <20230313151844.6eee28c6@kernel.org>
Date:   Mon, 13 Mar 2023 15:18:44 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Horatiu Vultur' <horatiu.vultur@...rochip.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "richardcochran@...il.com" <richardcochran@...il.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH net-next 2/2] net: lan966x: Stop using packing library

On Mon, 13 Mar 2023 17:04:11 +0000 David Laight wrote:
> It has to be possible to do much better that that.
> Given  that 'pos' and 'length' are always constants it looks like
> each call should reduce to (something like):
> 	ifh[k] |= val << n;
> 	ifk[k + 1] |= val >> (8 - n);
> 	...
> It might be that the compiler manages to do this, but I doubt it.

Agreed, going bit-by-bit seems overly cautious.