Re: [PATCH 02/16] i.MX: ocotp: Add provisions for storing multiple MAC addresses

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Stefan Lengfeld <s.lengfeld@phytec.de>
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>,
	"barebox@lists.infradead.org" <barebox@lists.infradead.org>
Subject: Re: [PATCH 02/16] i.MX: ocotp: Add provisions for storing multiple MAC addresses
Date: Wed, 7 Dec 2016 20:13:43 +0100	[thread overview]
Message-ID: <20161207191343.v2y3dmzo4m67ws3c@pengutronix.de> (raw)
In-Reply-To: <20161207085105.GC2371@lws-christ>

On Wed, Dec 07, 2016 at 09:51:05AM +0100, Stefan Lengfeld wrote:
> Hi Andrey,
> 
> > I did see that patch go through, however since the title of it is
> > "arm: imx6: ocotp: Added support for the i.MX6UL" I didn't look into
> > it any further.
> 
> In the light of the Vybrid also supports two MAC addresses your patch title
> 
>     i.MX: ocotp: Add provisions for storing multiple MAC addresses
> 
> is better, since it is more generic.
> 
> > > Your approach uses an extra device attribute  'mac_idx' to select the meaning
> > > of the device attribute 'mac_addr': Whether it points to the MAC0 or MAC1.
> > >
> > > I find it less error prone and confusing to use two seperate device attributes
> > > 'mac_addr' and 'mac_addr1' for MAC0 and MAC1. So you don't have to check the
> > > value of 'mac_idx before reading or writing the MAC addresses.
> > 
> > Can't say that I necessarily agree with you assessment. There's no
> > need to check 'mac_idx' if it is written every time as a part of MAC
> > address assignment operation. The reason I chose the approach that I
> > did was mainly because it allowed to both have backwards compatibility
> > with the old naming scheme and avoid having variable naming
> > inconsistency (as you see in your example where one variable has a
> > numerical suffix and the other doesn't) which I was concerned would be
> > make scripting it more clunky than necessary.
> 
> hmm, I find it more convenient use
> 
>     bootloader$ ocotp0.mac_addr=22:33:44:55:66:77
>     bootloader$ ocotp0.mac_addr1=22:33:44:AA:AA:AA
> 
> than 
> 
>     bootloader$ ocotp0.mac_idx=0
>     bootloader$ ocotp0.mac_addr=22:33:44:55:66:77
>     bootloader$ ocotp0.mac_idx=1
>     bootloader$ ocotp0.mac_addr=22:33:44:AA:AA:AA
> 
> The same goes for reading the MAC addresses. The first one is more obvious,
> because the meaning of the variable "mac_addr" does not depend on another
> variable "mac_idx".

I agree here.

> 
> Maybe we can settle on a different approach to avoid the inconsistent variable
> names "mac_addr" and "mac_addr1":

How about always registering mac_addr0 with mac_addr as alias? Then we
have consistent variable naming and still the backward compatible
standard mac address.

Sascha

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