netdev - Re: [PATCH net 5/5] net: ipa: avoid going past end of resource group array

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Date:   Wed, 28 Oct 2020 08:30:44 -0500
From:   Alex Elder <elder@...aro.org>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, evgreen@...omium.org,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net 5/5] net: ipa: avoid going past end of resource group
 array

On 10/27/20 7:14 PM, Willem de Bruijn wrote:
> On Tue, Oct 27, 2020 at 12:38 PM Alex Elder <elder@...aro.org> wrote:
>>
>> The minimum and maximum limits for resources assigned to a given
>> resource group are programmed in pairs, with the limits for two
>> groups set in a single register.
>>
>> If the number of supported resource groups is odd, only half of the
>> register that defines these limits is valid for the last group; that
>> group has no second group in the pair.
>>
>> Currently we ignore this constraint, and it turns out to be harmless,
> 
> If nothing currently calls it with an odd number of registers, is this
> a bugfix or a new feature (anticipating future expansion, I guess)?

. . .

Sorry, I missed this comment.  Yes, I'm working on support for
an upcoming IPA hardware version that has 5 resources of each
type.  And it is a bug fix, though the bug doesn't bite us
(because the maximum number of resources supported is even),
so "it turns out to be harmless."

					-Alex