From: David Collins <collinsd@codeaurora.org>
To: Stephen Warren <swarren@wwwdotorg.org>
Cc: devicetree-discuss@lists.ozlabs.org,
linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: How to represent negative values for device tree property
Date: Mon, 01 Apr 2013 17:24:19 -0700 [thread overview]
Message-ID: <515A2533.8050005@codeaurora.org> (raw)
In-Reply-To: <515A038F.2090902@wwwdotorg.org>
On 04/01/2013 03:00 PM, Stephen Warren wrote:
> On 04/01/2013 03:08 PM, David Collins wrote:
>> Hi,
>>
>> I am working on a thermal driver which needs to be able to read a
>> temperature threshold from a device tree property. The hardware supports
>> thresholds in the range -204.8 to +204.7 C in 0.1 C steps. I have found,
>> as I am sure others have as well, that dtc treats a '-' before an integer
>> in a dtsi file as a syntax error. Therefore, I need some artificial way
>> to represent negative numbers in device tree. Here are the possibilities
>> that I have thought of so far:
>
> Doesn't the very latest dtc, which contains integer expression support,
> allow unary -? I thought that code had been imported into the kernel
> (goes and checks) yes it has. What's the error you're seeing;
> over/underflow or syntax?
>
> That said, DT cells are supposed to be u32 not s32, so perhaps this
> isn't unexpected.
It is likely that my dtc version is out of date. dtc -v outputs 1.2.0. I
will try updating to a newer version of dtc. The error that I currently
get is a syntax error: "FATAL ERROR: Unable to parse input tree".
Does the device tree binary documentation define any format for negative
numbers? Unsigned 32-bit integers are clearly defined as bytes in
big-endian order. I suppose that you could assume 32-bit signed integers
are 2's complement with bytes in big-endian order, but that would need to
be well defined somewhere.
Assuming that dtb has no well defined means of holding a negative integer
value, then what is the most elegant workaround to specify a negative value?
--
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: collinsd@codeaurora.org (David Collins)
To: linux-arm-kernel@lists.infradead.org
Subject: How to represent negative values for device tree property
Date: Mon, 01 Apr 2013 17:24:19 -0700 [thread overview]
Message-ID: <515A2533.8050005@codeaurora.org> (raw)
In-Reply-To: <515A038F.2090902@wwwdotorg.org>
On 04/01/2013 03:00 PM, Stephen Warren wrote:
> On 04/01/2013 03:08 PM, David Collins wrote:
>> Hi,
>>
>> I am working on a thermal driver which needs to be able to read a
>> temperature threshold from a device tree property. The hardware supports
>> thresholds in the range -204.8 to +204.7 C in 0.1 C steps. I have found,
>> as I am sure others have as well, that dtc treats a '-' before an integer
>> in a dtsi file as a syntax error. Therefore, I need some artificial way
>> to represent negative numbers in device tree. Here are the possibilities
>> that I have thought of so far:
>
> Doesn't the very latest dtc, which contains integer expression support,
> allow unary -? I thought that code had been imported into the kernel
> (goes and checks) yes it has. What's the error you're seeing;
> over/underflow or syntax?
>
> That said, DT cells are supposed to be u32 not s32, so perhaps this
> isn't unexpected.
It is likely that my dtc version is out of date. dtc -v outputs 1.2.0. I
will try updating to a newer version of dtc. The error that I currently
get is a syntax error: "FATAL ERROR: Unable to parse input tree".
Does the device tree binary documentation define any format for negative
numbers? Unsigned 32-bit integers are clearly defined as bytes in
big-endian order. I suppose that you could assume 32-bit signed integers
are 2's complement with bytes in big-endian order, but that would need to
be well defined somewhere.
Assuming that dtb has no well defined means of holding a negative integer
value, then what is the most elegant workaround to specify a negative value?
--
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2013-04-02 0:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-01 21:08 How to represent negative values for device tree property David Collins
2013-04-01 21:08 ` David Collins
2013-04-01 22:00 ` Stephen Warren
2013-04-01 22:00 ` Stephen Warren
2013-04-02 0:24 ` David Collins [this message]
2013-04-02 0:24 ` David Collins
2013-04-02 6:29 ` David Gibson
2013-04-02 6:29 ` David Gibson
2013-04-02 15:36 ` Stephen Warren
2013-04-02 15:36 ` Stephen Warren
2013-04-02 6:17 ` David Gibson
2013-04-02 6:17 ` David Gibson
-- strict thread matches above, loose matches on Subject: below --
2013-03-29 20:13 David Collins
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