TipsAndTricks/QuickAndDirtyKernelConfig - Revision history

Bavery at 01:49, 1 November 2016

2016-11-01T01:49:02Z

← Older revision		Revision as of 01:49, 1 November 2016
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	<code>		<code>
	$grep -rH DMA_API_COW tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/		$grep -rH DMA_API_COW tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/.config:CONFIG_DMA_API_COW=y		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/.config:CONFIG_DMA_API_COW=y
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch.cfg:CONFIG_DMA_API_COW		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch.cfg:CONFIG_DMA_API_COW
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/invalid.cfg:CONFIG_DMA_API_COW		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/invalid.cfg:CONFIG_DMA_API_COW
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch-all.txt:Config: CONFIG_DMA_API_COW		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch-all.txt:Config: CONFIG_DMA_API_COW
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch-all.txt:Requested value: CONFIG_DMA_API_COW=y		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch-all.txt:Requested value: CONFIG_DMA_API_COW=y
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/merge_config_build.log:Value requested for CONFIG_DMA_API_COW not in final .config		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/merge_config_build.log:Value requested for CONFIG_DMA_API_COW not in final .config
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/merge_config_build.log:Requested value: CONFIG_DMA_API_COW=y		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/merge_config_build.log:Requested value: CONFIG_DMA_API_COW=y
	tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/configs/standard/intel/myKernelConfigs.cfg:CONFIG_DMA_API_COW=y		tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/configs/standard/intel/myKernelConfigs.cfg:CONFIG_DMA_API_COW=y
	</code>		</code>
	This tells us that the value CONFIG_DMA_API_COW is not in the final .config and is in the invalid.cfg file. Good to know!		This tells us that the value CONFIG_DMA_API_COW is not in the final .config and is in the invalid.cfg file. Good to know!

Bavery at 01:48, 1 November 2016

2016-11-01T01:48:40Z

← Older revision		Revision as of 01:48, 1 November 2016
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	CONFIG_DMA_API_DEBUG=y		CONFIG_DMA_API_DEBUG=y
	</code>		</code>
	It turns out that the CONFIG_DMA_API_COW option is not in the linux-yocto kernel. Big surprise! (This could also have been a ~~type~~, or an old config whose name got changed...).		It turns out that the CONFIG_DMA_API_COW option is not in the linux-yocto kernel. Big surprise! (This could also have been a typo, or an old config whose name got changed...).
	Config options that can't be applied for some reason appear in the file mismatch.cfg &/or invalid.cfg. These are in <code>tmp/work-shared/<machine>/kernel-source/.kernel-meta/ </code>.		Config options that can't be applied for some reason appear in the file mismatch.cfg &/or invalid.cfg. These are in <code>tmp/work-shared/<machine>/kernel-source/.kernel-meta/ </code>.
	This is a useful place to look when you set something and it doesn't seem to be taking effect. For instance:		This is a useful place to look when you set something and it doesn't seem to be taking effect. For instance:

Bavery: /* The Quick and Dirty Way */

2016-11-01T01:45:34Z

The Quick and Dirty Way

← Older revision		Revision as of 01:45, 1 November 2016
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	</code>		</code>
	The CONFIG_DMA_API_DEBUG got turned on as we hoped, yay!		The CONFIG_DMA_API_DEBUG got turned on as we hoped, yay!
			=== Something Can Go Wrong... ===
			This part is a silly example of how to tell what went wrong when you set config options. Let's suppose that I decide I also want to turn on the feature CONFIG_DMA_API_COW. I'm pretty certain that this is in my kernel so I'll just add it to the file myKernelConfigs.cfg:
			<code>
			# yes, comments are ok
			CONFIG_DMA_API_DEBUG=y
			# I'm pretty sure this is in my kernel
			CONFIG_DMA_API_COW=y
			</code>
			We can rm tmp and rerun <code> bitbake linux-yocto </code>. Sadly the grep of our config does not show a CONFIG_DMA_API_COW setting. Where did it go?
			<code>
			$grep CONFIG_DMA_API tmp/work/.../.config
			CONFIG_DMA_API_DEBUG=y
			</code>
			It turns out that the CONFIG_DMA_API_COW option is not in the linux-yocto kernel. Big surprise! (This could also have been a type, or an old config whose name got changed...).
			Config options that can't be applied for some reason appear in the file mismatch.cfg &/or invalid.cfg. These are in <code>tmp/work-shared/<machine>/kernel-source/.kernel-meta/ </code>.
			This is a useful place to look when you set something and it doesn't seem to be taking effect. For instance:
			<code>
			$grep -rH DMA_API_COW tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/.config:CONFIG_DMA_API_COW=y
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch.cfg:CONFIG_DMA_API_COW
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/invalid.cfg:CONFIG_DMA_API_COW
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch-all.txt:Config: CONFIG_DMA_API_COW
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/mismatch-all.txt:Requested value: CONFIG_DMA_API_COW=y
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/merge_config_build.log:Value requested for CONFIG_DMA_API_COW not in final .config
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/cfg/merge_config_build.log:Requested value: CONFIG_DMA_API_COW=y
			tmp/work-shared/intel-corei7-64/kernel-source/.kernel-meta/configs/standard/intel/myKernelConfigs.cfg:CONFIG_DMA_API_COW=y
			</code>
			This tells us that the value CONFIG_DMA_API_COW is not in the final .config and is in the invalid.cfg file. Good to know!

Bavery at 01:33, 1 November 2016

2016-11-01T01:33:31Z

← Older revision		Revision as of 01:33, 1 November 2016
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	and nothing else. What can I do then? With the standard settings, we get:		and nothing else. What can I do then? With the standard settings, we get:
	<code>		<code>
	$grep ~~DMA_API_DEBUG~~ tmp/work/.../.config		$grep CONFIG_DMA_API tmp/work/.../.config
	# CONFIG_DMA_API_DEBUG is not set		# CONFIG_DMA_API_DEBUG is not set
	</code>		</code>
Line 32:		Line 32:
	SRC_URI_append_pn-linux-yocto = " file://myKernelConfigs.cfg "		SRC_URI_append_pn-linux-yocto = " file://myKernelConfigs.cfg "
	</code>		</code>
	The file myKernelConfigs.cfg is in my conf directory. I could have put it anywhere I wanted, even into a separate git repo in ~/kernelconfigsrepo, for example. myKernelConfigs.cfg contains the kernel configs I want to set. ~~In this example it~~'s ~~pretty simple~~:		The file myKernelConfigs.cfg is in my conf directory. I could have put it anywhere I wanted, even into a separate git repo in ~/kernelconfigsrepo, for example. myKernelConfigs.cfg contains the kernel configs I want to set. Let's suppose I want to turn on CONFIG_DMA_API_DEBUG.
			So the file myKernelConfigs.cfg would have:
	<code>		<code>
	# yes, comments are ok		# yes, comments are ok
Line 39:		Line 40:
	If I delete the tmp folder and rerun <code> bitbake linux-yocto </code> I can then see the following:		If I delete the tmp folder and rerun <code> bitbake linux-yocto </code> I can then see the following:
	<code>		<code>
	$grep ~~DMA_API_DEBUG~~ tmp/work/.../.config		$grep CONFIG_DMA_API tmp/work/.../.config
			CONFIG_DMA_API_DEBUG=y
	</code>		</code>
			The CONFIG_DMA_API_DEBUG got turned on as we hoped, yay!

Bavery at 01:13, 1 November 2016

2016-11-01T01:13:42Z

← Older revision		Revision as of 01:13, 1 November 2016
Line 2:		Line 2:

	== The Real Way ==		== The Real Way ==
	The best in depth explanation/tutorial for working with the kernel in Yocto is located here: https://www.yoctoproject.org/training/kernel-lab. It has a pdf, and supporting layers/metadata to allow you to follow along. If you are going to do a lot with the kernel or are planning to ship it in a product/project, I'd strongly recommend going through the lab.		The best in depth explanation/tutorial for working with the kernel in Yocto is located here: https://www.yoctoproject.org/training/kernel-lab. It has a pdf, and supporting layers/metadata to allow you to follow along. There is also a kernel development manual located at http://www.yoctoproject.org/docs/latest/kernel-dev/kernel-dev.html.
			<br>
			If you are going to do a lot with the kernel or are planning to ship it in a product/project, I'd strongly recommend going through the lab and reading the kernel manual.

	== The Quick and Dirty Way ==		== The Quick and Dirty Way ==
Line 8:		Line 10:
	=== Menuconfig ===		=== Menuconfig ===
	<code>bitbake linux-yocto -c menuconfig </code>		<code>bitbake linux-yocto -c menuconfig </code>
	~~Will~~ put you into ~~hte~~ standard ncurses menuconfig screen and you can select options as normal and then rebuild your kernel with:		This will put you into the standard ncurses menuconfig screen and you can select options as normal and then rebuild your kernel with:
	<code>bitbake linux-yocto </code>		<code>bitbake linux-yocto </code>
	This will modify the .config file that linux-yocto uses		This will modify the .config file that linux-yocto uses

Bavery: Created page with "= How to Quickly Set Some Options in the Kernel = == The Real Way == The best in depth explanation/tutorial for working with the kernel in Yocto is located here: https://www..."

2016-11-01T01:09:57Z

Created page with "= How to Quickly Set Some Options in the Kernel = == The Real Way == The best in depth explanation/tutorial for working with the kernel in Yocto is located here: https://www..."

New page

= How to Quickly Set Some Options in the Kernel =

== The Real Way ==
The best in depth explanation/tutorial for working with the kernel in Yocto is located here: https://www.yoctoproject.org/training/kernel-lab. It has a pdf, and supporting layers/metadata to allow you to follow along. If you are going to do a lot with the kernel or are planning to ship it in a product/project, I'd strongly recommend going through the lab.

== The Quick and Dirty Way ==
But, sometimes, you really just want to be able to set an option. How can you do this?
=== Menuconfig ===
<code>bitbake linux-yocto -c menuconfig </code>
Will put you into hte standard ncurses menuconfig screen and you can select options as normal and then rebuild your kernel with:
<code>bitbake linux-yocto </code>
This will modify the .config file that linux-yocto uses
<code>tmp/work/<machine>-common-poky-linux/linux-yocto/<version>/linux-<machine>-common-standard-build/.config </code>
in the version I am working off of it looks like this for a machine=intel-corei7-64 and a linux-yocto near the time of Morty's (YP 2.2) release.
<code>tmp/work/corei7-64-intel-common-poky-linux/linux-yocto/4.8+gitAUTOINC+552a83790b_67813e7efa-r0/linux-corei7-64-intel-common-standard-build/.config</code>
The good news is that that was pretty easy. The bad news, is that
* if I remove tmp, as I tend to do, then my .config will go away.
* if I want to share my additions with someone else, I need to give them a whole .config file and tell them to read the above referenced lab for how to use it.
=== Just the Configs I want, nothing more ===
Suppose I <strong>know</strong> that I just want to set
<code>CONFIG_DMA_API_DEBUG=y</code>
and nothing else. What can I do then? With the standard settings, we get:
<code>
$grep DMA_API_DEBUG tmp/work/.../.config
# CONFIG_DMA_API_DEBUG is not set
</code>
So, the Quick & Dirty approach is to add the following to the end of my conf/local.conf file:
<code>
FILESEXTRAPATHS_prepend_pn-linux-yocto := "/my/absolute/path/build/conf:"
SRC_URI_append_pn-linux-yocto = " file://myKernelConfigs.cfg "
</code>
The file myKernelConfigs.cfg is in my conf directory. I could have put it anywhere I wanted, even into a separate git repo in ~/kernelconfigsrepo, for example. myKernelConfigs.cfg contains the kernel configs I want to set. In this example it's pretty simple:
<code>
# yes, comments are ok
CONFIG_DMA_API_DEBUG=y
</code>
If I delete the tmp folder and rerun <code> bitbake linux-yocto </code> I can then see the following:
<code>
$grep DMA_API_DEBUG tmp/work/.../.config

</code>