[OE-core] [oe] staging & using kernel headers

[Michael Jones]

Sorry for the delay, I overlooked the last 2 replies because I was no
longer in to: or cc:  :(

On 03/28/2011 02:42 PM, Richard Purdie wrote:
> On Fri, 2011-03-25 at 17:02 +0100, Michael Jones wrote:
>> On 03/25/2011 03:55 PM, Richard Purdie wrote:
>>> On Fri, 2011-03-25 at 15:14 +0100, Michael Jones wrote:
>>> Ok, so you only really have the options of:
>>>
>>> a) Use a specific patched kernel for linux-libc-headers which has these
>>> headers in it (see below for why this is ugly)
>>> b) Install some extra headers in "libc-headers-extras" type recipe
>>> c) Ship default versions of the headers with your userspace and use
>>> those if shared versions don't exist. This assumes the API is stable and
>>> on its way to mainline.
>>>
>>> I don't think this is as common a requirement as you think as most
>>> people get this kind of thing merged into the mainline kernel to try and
>>> reduce this kind of problem.
>>
>> To clarify, it's not that I have a custom patched kernel I need to use.
>>  I am following V4L2 development, so I am using a new kernel from those
>> developers.  V4L2 changes do of course move upstream.
> 
> Ok, sorry, I was lacking context here.
>  
>>> The ugliness is where you have two different arm boards you want to
>>> build, with a common optimisation/toolchain and each wants to redirect
>>> linux-libc-headers to its own "special" version. The question is then,
>>> why aren't the "special" bits in mainline.
>>
>> OK, so here's what I'm realizing, please correct me if I'm wrong:
>> What I did unconventionally (ie. wrong) was to use a kernel version
>> newer than my linux-libc-headers were.  I should create a new
>> linux-libc-headers recipe, as I had done with the kernel recipe, and
>> build glibc and linux-libc-headers using my 2.6.38 kernel.
> 
> We should *always* be using linux-libc-headers >= to the kernel version
> being used.

Isn't it the other way around?  Steffen Sledz had the opposite problem
as me in Feb
(http://www.mail-archive.com/openembedded-devel%40lists.openembedded.org/msg16022.html)
because he's using a kernel older than the linux-libc-headers.  He
quotes the kernel doc: "This means that a program built against a C
library using older kernel headers should run on a newer kernel"

> 
>> I only stumbled upon this because the gstreamer-ti recipes were pointing
>> at internal kernel headers, but because these are user-space apps, they
>> should actually be using the linux-libc-headers.  Right?
> 
> Ideally, yes. I know under some circumstances, they might want to poke
> into internal kernel headers but that is really a design issue that
> needs fixing.
> 
> Cheers,
> 
> Richard
> 

-Michael


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