netdev - Re: [PATCH/RFC net-next 3/5] ravb: do not write 1 to reserved bits

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Message-Id: <20180417.101553.1512039208518397234.davem@davemloft.net>
Date:   Tue, 17 Apr 2018 10:15:53 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     horms+renesas@...ge.net.au
Cc:     sergei.shtylyov@...entembedded.com, magnus.damm@...il.com,
        netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        wsa+renesas@...g-engineering.com, kazuya.mizuguchi.ks@...esas.com
Subject: Re: [PATCH/RFC net-next 3/5] ravb: do not write 1 to reserved bits

From: Simon Horman <horms+renesas@...ge.net.au>
Date: Tue, 17 Apr 2018 10:50:28 +0200

> From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> 
> This patch corrects writing 1 to reserved bits.
> The write value should be 0.
> 
> Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>

How are we ending up in situations where the driver is trying to write
non-zero values to those fields in the first place?

The places creating those values should be making sure that the
reserved bits are never set.

If you mask out the reserved bits in the register writing locations,
this just hides bugs.