linux-kernel - Re: [PATCH net-next] net: ipa: avoid 64-bit modulus

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Date:   Wed, 24 Mar 2021 12:32:25 -0500
From:   Alex Elder <elder@...aro.org>
To:     David Laight <David.Laight@...LAB.COM>,
        'Alex Elder' <elder@...e.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
Cc:     "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "evgreen@...omium.org" <evgreen@...omium.org>,
        "cpratapa@...eaurora.org" <cpratapa@...eaurora.org>,
        "subashab@...eaurora.org" <subashab@...eaurora.org>,
        "elder@...nel.org" <elder@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] net: ipa: avoid 64-bit modulus

On 3/24/21 12:12 PM, David Laight wrote:
> I think 'count' is also required to be a power of 2.
> so you could have checked 'addr & (size - 1)'.

It is required to be, and that is checked elsewhere
(in gsi_channel_data_valid()).  And yes, size would
therefore be a power-of-2, and so your clever test
would be a simple test.

I'll take that into account when I implement the
fix.  Thanks for the suggestion.

					-Alex