linux-kernel - Re: [PATCH] of: support passing console options with stdout-path

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Message-ID: <20141124230016.GP20238@lunn.ch>
Date:	Tue, 25 Nov 2014 00:00:16 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Leif Lindholm <leif.lindholm@...aro.org>
Cc:	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, mark.rutland@....com,
	grant.likely@...aro.org, robh+dt@...nel.org, plagnioj@...osoft.com,
	ijc@...ian.org
Subject: Re: [PATCH] of: support passing console options with stdout-path

On Mon, Nov 24, 2014 at 10:23:58PM +0000, Leif Lindholm wrote:
> Support specifying console options (like with console=ttyXN,<options>)
> by appending them to the stdout-path property after a separating ':'.
> 
> Example:
> 	stdout-path = "uart0:115200";
> 
> This patch also modifies of_find_node_by_path() to match only the
> portion of the path before a ':'.

Hi Leif

These appears to somewhat conform to ePAPR, which says:

      A string that specifies the full path to the node representing
      the device to be used for boot console output. If the character
      ":" is present in the value it terminates the path.

So you can put any random junk after the :. However, are we going to
have backward/forward compatibility problems, and problems with
bootloaders? The current kernel code does not look for the :. So a new
DT blob on an old kernel will not work so well.

More worrying, barebox does not support the : either. So there is a
danger your bootloader suddenly goes silent after a dt blob update.

Would it be safer to add a new property in chosen?

      Andrew
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