[yocto] basic questions on LINUX costomization for raspberrypi

[Jim Rafert]

Hello Abhishek,

Here's some more information to supplement what Andrei wrote.

The Yocto build system is based upon OpenEmbedded (OE), which depends upon
bitbake recipes to build everything from the kernel to applications.  Recipes are gathered
into layers,  which provide some aggregate functionality.  For example, the software required to support the Raspberry Pi hardware is collected in the meta-raspberrypi layer. So, if you want
to add something to your Linux build, it's generally just a a matter of finding the correct
recipe, and any recipes it may depend upon, and adding it into your IMAGE_INSTALL_append variable in the local.conf file.  If the recipe is not included in any of the layers that you are already using, you may have to create a custom layer of your own and add the recipe in there.
If you can't find the recipe that you need in any of the meta* directories, google can be of great help.

If you have not already, you should read the Yocto project quick start manual.
http://www.yoctoproject.org/docs/current/yocto-project-qs/yocto-project-qs.html

The process of configuring the kernel is covered in the kernel development manual.
http://www.yoctoproject.org/docs/1.6.1/kernel-dev/kernel-dev.html

When you make any changes to configuration or software, you will have to rebuild the particular
image that you are using, so that the changes will be incorporated into the filesystem images.
Because dependencies are generally well specified in Yocto, builds after the first build will be much
faster because much of the work is already done.

Speaking of images, you should do some research into which pre-configured image is closest to your
final desired result, without packing in too much stuff that you don't need.  The core-image-minimal
image can be a good start, but it is truly minimal, probably requiring a great deal of work to add
what you need for your desired configuration.  For instance, I found it convenient to start with core-image-full-cmdline, because I needed a fairly full command line experience for my applications, but did not need a graphical display.l


________________________________
From: Andrei Gherzan [andrei at gherzan.ro]
Sent: Tuesday, January 13, 2015 4:57 PM
To: abhishek srivastava
Cc: yocto at yoctoproject.org
Subject: Re: [yocto] basic questions on LINUX costomization for raspberrypi

Hello,

Please read the meta-raspberrypi README for basic information and use .
http://git.yoctoproject.org/cgit/cgit.cgi/meta-raspberrypi/tree/README

1) it depends on the image you are baking. What do you mean by reference list?
2) IMAGE_INSTALL_append http://www.yoctoproject.org/docs/current/ref-manual/ref-manual.html#var-IMAGE_INSTALL
What process are you talking about?
3) You modify the kernel config, recompile the kernel and then the image. We are developing a better way to configure kernel. Is already in review - hope to get some time for that soon.
4) Applications should be packages, right? Could you please rephrase your question?

Cheers!

On Thu, Dec 18, 2014 at 8:10 PM, abhishek srivastava <just_abhi22 at yahoo.co.in<mailto:just_abhi22 at yahoo.co.in>> wrote:
Hi allPlease answer to these questions regarding LINUX kernel image build using yocto project:
1) What basic LINUX packages needed for raspberrypi ? any list for reference ?
2) What if I want to add any package after my image is build ? Do i need to repeat the complete process again?
3) How can i add any driver (ex: TFT driver) to the build kernel image?
4) How to add any desired applications to packages?

Thank you for your help

regards

Abhishek


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