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authorScott Rifenbark <scott.m.rifenbark@intel.com>2011-07-27 12:59:10 -0700
committerRichard Purdie <richard.purdie@linuxfoundation.org>2011-08-04 15:06:47 +0100
commit05b0b88882269d55d8229c98f7cac20a67ef149a (patch)
tree4df91899539069fe04fe536ba619d8ce7ba9399c /documentation/dev-manual
parent4737719dc196f98aef768fd814c96adfe1069759 (diff)
downloadpoky-05b0b88882269d55d8229c98f7cac20a67ef149a.tar.gz
documentation/dev-manual/dev-manual-cases.xml: removed BSP overview.
this is now in the model chapter. Eventually the cases chapter will disappear. (From yocto-docs rev: fde20eede9f04899b61742b05ce73c97b2737bf3) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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5 5
6<title>Development Cases</title> 6<title>Development Cases</title>
7 7
8<para>
9 Many development cases exist for which you can use the Yocto Project.
10 However, for the purposes of this manual we are going to focus on two common development cases or groupings:
11 System Development and User Application Development.
12 System Development covers Board Support Package (BSP) development and kernel modification.
13 User Application Development covers development of applications that you intend to run on some
14 target hardware.
15</para>
16
17<para>
18 This chapter presents an overview of the primary cases.
19 Supsequent appendices in the manual provide detailed explanations of the examples.
20</para>
21
22<para>
23 [WRITERS NOTE: What is undetermined at this point is how much of the entire development process
24 we include in this particular chapter.
25 In other words, do we cover debugging and emulation steps here on a case-specific basis?
26 Or, do we capture that information in the appropriate subsequent chapter by case?]
27</para>
28
29<section id='system-development'>
30 <title>System Development</title>
31
32 <para>
33 System development involves modification or creation of an image that you want to run on
34 a specific hardware target.
35 Usually when you want to create an image that runs on embedded hardware the image does
36 not require the same amount of features that a full-fledged Linux distribution provides.
37 Thus, you can create a much smaller image that is designed to just use the hardware
38 features for your particular hardware.
39 </para>
40
41 <para>
42 To help you understand how system development works in the Yocto Project, this section
43 covers two types of image development: BSP creation and kernel modification.
44 </para>
45
46 <section id='developing-a-board-support-package-bsp'>
47 <title>Developing a Board Support Package (BSP)</title>
48
49 <para>
50 A BSP is a package of recipes that when applied while building an image results in
51 an image you can run on a particular board.
52 Thus, the package, when compiled into the new image, supports the operation of the board.
53 </para>
54
55 <note>
56 For a brief list of terms used when describing the development process in the Yocto Project,
57 see <xref linkend='yocto-project-terms'>Yocto Project Terms</xref> in this manual.
58 </note>
59
60 <para>
61 The remainder of this section presents the basic steps to create a BSP basing it on an
62 existing BSP that ships with the Yocto Project.
63 You can reference <xref linkend='dev-manual-bsp-appendix'>BSP Development Case</xref>
64 for a detailed example that uses the Crown Bay BSP as a base BSP from which to start.
65 </para>
66
67 <para>
68 Here are the basic steps involved in creating a BSP:
69 <orderedlist>
70 <listitem><para><emphasis>Set up your host development system to support
71 development using the Yocto Project</emphasis>: See
72 <ulink url='http://www.yoctoproject.org/docs/1.1/yocto-project-qs/yocto-project-qs.html#the-linux-distro'>
73 The Linux Distributions</ulink> section and
74 <ulink url='http://www.yoctoproject.org/docs/1.1/yocto-project-qs/yocto-project-qs.html#packages'>
75 The Packages</ulink> section both
76 in the Yocto Project Quick Start for requirements.
77 You will also need a release of Yocto Project installed on the host.</para></listitem>
78 <listitem><para><emphasis>Establish a local copy of the Yocto Project files on your
79 system</emphasis>: You need to have the Yocto Project files available on your host system.
80 Having the Yocto Project files on your system gives you access to the build
81 process and tools you need.
82 For information on how to get these files, see the
83 <xref linkend='getting-setup'>Getting Setup</xref> section in this manual.</para></listitem>
84 <listitem><para><emphasis>Choose a Yocto Project-supported BSP as your base BSP</emphasis>:
85 The Yocto Project ships with several BSPs that support various hardware.
86 It is best to base your new BSP on an existing BSP rather than create all the
87 recipes and configuration files from scratch.
88 While it is possible to create everything from scratch, basing your new BSP
89 on something that is close is much easier.
90 Or, at a minimum, it gives you some structure with which to start.</para>
91 <para>At this point you need to understand your target hardware well enough to determine which
92 existing BSP it most closely matches.
93 Things to consider are your hardware’s on-board features such as CPU type and graphics support.
94 You should look at the README files for supported BSPs to get an idea of which one
95 you could use.
96 A generic Atom-based BSP to consider is the Crown Bay that does not support
97 the Intel® Embedded Media Graphics Driver (EMGD).
98 The remainder of this example uses that base BSP.</para>
99 <para>To see the supported BSPs, go to the Yocto Project
100 <ulink url='http://www.yoctoproject.org/download'>download page</ulink> and click
101 on “BSP Downloads.”</para></listitem>
102 <listitem><para><emphasis>Establish a local copy of the base BSP files</emphasis>: Having
103 the BSP files on your system gives you access to the build
104 process and tools you need.
105 For information on how to get these files, see
106 <xref linkend='getting-setup'>Getting Setup</xref> earlier in this manual.</para></listitem>
107 <listitem><para><emphasis>Create your own BSP layer</emphasis>: Layers are ideal for
108 isolating and storing work for a given piece of hardware.
109 A layer is really just a location or area in which you place the recipes for your BSP.
110 In fact, a BSP is, in itself, a special type of layer.
111 Consider an application as another example that illustrates a layer.
112 Suppose you are creating an application that has library or other dependencies in
113 order for it to compile and run.
114 The layer, in this case, would be where all the recipes that define those dependencies
115 are kept. The key point for a layer is that it is an isolated area that contains
116 all the relevant information for the project that the Yocto Project build
117 system knows about.</para>
118 <note>The Yocto Project supports four BSPs that are part of the
119 Yocto Project release: <filename>atom-pc</filename>, <filename>beagleboard</filename>,
120 <filename>mpc8315e</filename>, and <filename>routerstationpro</filename>.
121 The recipes and configurations for these four BSPs are located and dispersed
122 within local Yocto Project files.
123 Consequently, they are not totally isolated in the spirit of layers unless you think
124 of <filename>meta-yocto</filename> as a layer itself.
125 On the other hand, BSP layers for Crown Bay, Emenlow, Jasper Forest,
126 N450, and Sugar Bay are isolated.</note>
127 <para>When you set up a layer for a new BSP you should follow a standard layout.
128 This layout is described in the
129 <ulink url='http://www.yoctoproject.org/docs/1.1/bsp-guide/bsp-guide.html#bsp-filelayout'>
130 Example Filesystem Layout</ulink> section of the Board Support Package (BSP) Development
131 Guide.
132 In the standard layout you will notice a suggested structure for recipes and
133 configuration information.
134 You can see the standard layout for the Crown Bay BSP in this example by examining the
135 directory structure of the <filename>meta-crownbay</filename> layer inside the
136 local Yocto Project files.</para></listitem>
137 <listitem><para><emphasis>Make configuration and recipe changes to your new BSP
138 layer</emphasis>: The standard BSP layer structure organizes the files you need to edit in
139 <filename>conf</filename> and several <filename>recipes-*</filename> within the
140 BSP layer.</para>
141 <para>Configuration changes identify where your new layer is on the local system
142 and identify which kernel you are going to use.
143 Recipe changes include altering recipes (<filename>.bb</filename> files), removing
144 recipes you don't use, and adding new recipes that you need to support your hardware.
145 </para></listitem>
146 <listitem><para><emphasis>Prepare for the build</emphasis>: Once you have made all the
147 changes to your BSP layer there remains a few things
148 you need to do for the Yocto Project build system in order for it to create your image.
149 You need to get the build environment ready by sourcing an environment setup script
150 and you need to be sure two key configuration files are configured appropriately.</para>
151 <para>The entire process for building an image is overviewed in the
152 <ulink url='http://www.yoctoproject.org/docs/1.1/yocto-project-qs/yocto-project-qs.html#building-image'>
153 Building an Image</ulink> section of the Yocto Project Quick Start.
154 You might want to reference this information.</para></listitem>
155 <listitem><para><emphasis>Build the image</emphasis>: The Yocto Project uses the BitBake
156 tool to build images based on the type of image
157 you want to create.
158 You can find more information on BitBake
159 <ulink url='http://bitbake.berlios.de/manual/'>here</ulink>.</para>
160 <para>The build process supports several types of images to satisfy different needs.
161 When you issue the BitBake command you provide a “top-level” recipe that essentially
162 starts the process off of building the type of image you want.</para>
163 <para>[WRITER'S NOTE: Consider moving this to the Poky Reference Manual.]</para>
164 <para>You can find these recipes in the <filename>meta/recipes-core/images</filename> and
165 <filename>meta/recipes-sato/images</filename> directories of your local Yocto Project
166 file structure (Git repository or extracted release tarball).
167 Although the recipe names are somewhat explanatory, here is a list that describes them:
168 <itemizedlist>
169 <listitem><para><emphasis>Base</emphasis> – A foundational basic image without support
170 for X that can be reasonably used for customization.</para></listitem>
171 <listitem><para><emphasis>Core</emphasis> – A foundational basic image with support for
172 X that can be reasonably used for customization.</para></listitem>
173 <listitem><para><emphasis>Direct Disk</emphasis> – An image that you can copy directory to
174 the disk of the target device.</para></listitem>
175 <listitem><para><emphasis>Live</emphasis> – An image you can run from a USB device or from
176 a CD without having to first install something.</para></listitem>
177 <listitem><para><emphasis>Minimal</emphasis> – A small image without a GUI.
178 This image is not much more than a kernel with a shell.</para></listitem>
179 <listitem><para><emphasis>Minimal Development</emphasis> – A Minimal image suitable for
180 development work.</para></listitem>
181 <listitem><para><emphasis>Minimal Direct Disk</emphasis> – A Minimal Direct
182 Disk image.</para></listitem>
183 <listitem><para><emphasis>Minimal RAM-based Initial Root Filesystem</emphasis> –
184 A minimal image
185 that has the <filename>initramfs</filename> as part of the kernel, which allows the
186 system to find the first “init” program more efficiently.</para></listitem>
187 <listitem><para><emphasis>Minimal Live</emphasis> – A Minimal Live image.</para></listitem>
188 <listitem><para><emphasis>Minimal MTD Utilities</emphasis> – A minimal image that has support
189 for the MTD utilities, which let the user interact with the MTD subsystem in
190 the kernel to perform operations on flash devices.</para></listitem>
191 <listitem><para><emphasis>Sato</emphasis> – An image with Sato support, a mobile environment
192 and visual style that works well with mobile devices.</para></listitem>
193 <listitem><para><emphasis>Sato Development</emphasis> – A Sato image suitable for
194 development work.</para></listitem>
195 <listitem><para><emphasis>Sato Direct Disk</emphasis> – A Sato Direct
196 Disk image.</para></listitem>
197 <listitem><para><emphasis>Sato Live</emphasis> – A Sato Live image.</para></listitem>
198 <listitem><para><emphasis>Sato SDK</emphasis> – A Sato image that includes the Yocto Project
199 toolchain and development libraries.</para></listitem>
200 <listitem><para><emphasis>Sato SDK Direct Disk</emphasis> – A Sato SDK Direct
201 Disk image.</para></listitem>
202 <listitem><para><emphasis>Sato SDK Live</emphasis> – A Sato SDK Live
203 image.</para></listitem>
204 </itemizedlist>
205 </para></listitem>
206 </orderedlist>
207 </para>
208
209 <para>
210 You can view a video presentation of the BSP creation process
211 <ulink url='http://free-electrons.com/blog/elc-2011-videos'>here</ulink>.
212 You can also find supplemental information in the
213 <ulink url='http://yoctoproject.org/docs/1.1/bsp-guide/bsp-guide.html'>
214 Board Support Package (BSP) Development Guide</ulink>.
215 Finally, there is wiki page write up of the example located
216 <ulink url='https://wiki.yoctoproject.org/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>
217 here</ulink> you might find helpful.
218 </para>
219 </section>
220
221 <section id='modifying-a-kernel-kernel-example'> 8 <section id='modifying-a-kernel-kernel-example'>
222 <title>Modifying a Kernel</title> 9 <title>Modifying a Kernel</title>
223 10
@@ -593,7 +380,6 @@
593 </section> 380 </section>
594 </section> 381 </section>
595 </section> 382 </section>
596</section>
597 383
598</chapter> 384</chapter>
599 385
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