Message-ID: <51A42ED5.2060104@wwwdotorg.org>
Date: Mon, 27 May 2013 22:13:09 -0600
From: Stephen Warren <swarren@wwwdotorg.org>
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To: Alexandre Courbot <acourbot@nvidia.com>
CC: Andrew Morton <akpm@linux-foundation.org>, Arnd Bergmann <arnd@arndb.de>,
        Olof Johansson <olof@lixom.net>, Rob Clark <robclark@gmail.com>,
        linux-fbdev@vger.kernel.org, devicetree-discuss@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org,
        linux-rpi-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        gnurou@gmail.com
Subject: Re: [PATCH v2] video: simplefb: add mode parsing function
References: <1369626821-28494-1-git-send-email-acourbot@nvidia.com>
In-Reply-To: <1369626821-28494-1-git-send-email-acourbot@nvidia.com>
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On 05/26/2013 09:53 PM, Alexandre Courbot wrote:
> The naming scheme of simplefb's mode is precise enough to allow building
> the mode structure from it instead of using a static list of modes. This
> patch introduces a function that does this. In case exotic modes that
> cannot be represented from their name alone are needed, the static list
> of modes is still available as a backup.
> 
> It also changes the order in which colors are declared from MSB first to
> the more standard LSB first.
> 
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
> Changes from v1:
> - amended documentation following Stephen's suggestion
> - allow parsing of bitfields larger than 9 bits
> - made it clear that the parsing order of bits is changed with respect
>   to the original patch
> 
> Andrew, since this patch introduces a (small) change in the DT bindings,
> could we try to merge it during the -rc cycle so we don't have to come
> with a more complex solution in the future?

So, I think we shouldn't change the DT binding at all now. The original
driver is now merged for 3.10, and I think it's far too late to take
code that implements new features for 3.10. This means that we couldn't
merge this patch until 3.11. However, by then, we shouldn't be changing
the DT binding in incompatible ways. Olof has already published some
U-Boot binaries that use the current binding, and on IRC indicated he'd
prefer not to change the binding because of that.

As such, we should either:

a) Just add new entries into the format array that already exists in the
driver. Given David's response, this might be simplest.

b) Extend the DT binding in a 100% backwards-compatible way, which would
mean defaulting the bit-order to match the existing 1 format, and adding
a new Boolean property to indicate that the format string is specified
in the other order.
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