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authorScott Rifenbark <scott.m.rifenbark@intel.com>2011-08-03 12:05:32 -0700
committerRichard Purdie <richard.purdie@linuxfoundation.org>2011-08-15 15:26:58 +0100
commitfa1fb04bbb73e45b146d0715d6131434887d4d00 (patch)
treec97bfcfe429e57e21d029901f51b89324cc16e8c /documentation
parent07544deddca6a885be0133a0a5da89f2e1a365e0 (diff)
downloadpoky-fa1fb04bbb73e45b146d0715d6131434887d4d00.tar.gz
documentation/dev-manual/dev-manual-kernel-appendix.xml: partial updates
various things going on in the kernel example. Far from complete. (From yocto-docs rev: 0c0548b79589a606f91bdb39e5a2ece71f4c108e) 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>Kernel Modification Example</title> 6<title>Kernel Modification Example</title>
7 7
8 <para>
9 Kernel modification involves changing or adding configurations to an existing kernel, or
10 adding recipes to the kernel that are needed to support specific hardware features.
11 The process is similar to creating a Board Support Package (BSP) except that it invloves
12 isolating your work in a kernel layer and the use of <filename>menuconfig</filename>
13 to help make configuration data easily identifiable.
14 </para>
15
16 <para>
17 This section presents a simple example that shows how to modify the kernel.
18 The example uses a three-step approach that is convenient for making kernel modifications.
19 <orderedlist>
20 <listitem><para>Iteratively determine and set kernel configurations and make
21 kernel recipe changes.</para></listitem>
22 <listitem><para>Apply your configuration changes to your local kernel layer.
23 </para></listitem>
24 <listitem><para>Push your configuration and recipe changes upstream into the
25 Yocto Project source repositories to make them available to the community.
26 </para></listitem>
27 </orderedlist>
28 </para>
29
30 <section id='modifying-a-kernel-example'>
31 <title>Modifying a Kernel Example</title>
32
8 <para> 33 <para>
9 Kernel modification involves changing or adding configurations to an existing kernel, or 34 The example changes kernel configurations to support the VFAT filesystem and
10 adding recipes to the kernel that are needed to support specific hardware features. 35 allow the user to print out a simple text file from the mounted VFAT filesystem.
11 The process is similar to creating a Board Support Package (BSP) except that it invloves 36 The filesystem used will be an image filesystem rather than a filesystem on some
12 isolating your work in a kernel layer and the use of <filename>menuconfig</filename> 37 external drive such as a USB stick or external drive.
13 to help make configuration data easily identifiable. 38 The example uses the <filename>linux-yocto-2.6.37</filename> kernel.
14 </para> 39 </para>
15 40
16 <para> 41 <para>
17 This section presents a brief overview of the kernel structure and then provides a simple 42 For a general flow of the example, see
18 example that shows how to modify the kernel. 43 <xref linkend='kernel-modification-workflow'>Kernel Modification Workflow</xref>
44 earlier in this manual.
19 </para> 45 </para>
20 46
21 <section id='yocto-project-kernel'> 47 <section id='setting-up-yocto-project-kernel-example'>
22 <title>Yocto Project Kernel Overview</title> 48 <title>Setting Up Yocto Project</title>
23 49
24 <para> 50 <para>
25 When one thinks of the source files for a kernel they usually think of a fixed structure 51 You need to have the Yocto Project files available on your host system.
26 of files that contain kernel patches. 52 You can get files through tarball extraction or by cloning the <filename>poky</filename>
27 The Yocto Project, however, employs mechanisims that in a sense result in a kernel source 53 Git repository.
28 generator. 54 See the bulleted item
55 <link linkend='local-yp-release'>Yocto Project Release</link> in
56 <xref linkend='getting-setup'>Getting Setup</xref> earlier in this manual
57 for information on how to get these files.
29 </para> 58 </para>
30 59
31 <para> 60 <para>
32 The Yocto Project uses the source code management (SCM) tool Git to manage and track Yocto 61 Once you have the local <filename>poky</filename> Git repository set up,
33 Project files. 62 you have many development branches from which you can work.
34 Git employs branching strategies that effectively produce a tree-like structure whose 63 From inside the repository you can see the branch names and the tag names used
35 branches represent diversions from more general code. 64 in the Git repository using either of the following two commands:
36 For example, suppose two kernels are basically identical with the exception of a couple 65 <literallayout class='monospaced'>
37 different features in each. 66 $ git branch -a
38 In the Yocto Project source repositories managed by Git a main branch can contain the 67 $ git tag -l
39 common or shared 68 </literallayout>
40 parts of the kernel source and two branches that diverge from that common branch can 69 For this example we are going to use the Yocto Project 1.1 Release,
41 each contain the features specific to the respective kernel. 70 which maps to the <filename>1.1</filename> branch in the repository.
42 The result is a managed tree whose "leaves" represent the end of a specific path that yields 71 These commands create a local branch named <filename>1.1</filename>
43 a set of kernel source files necessary for a specific piece of hardware and its features. 72 that tracks the remote branch of the same name.
73 <literallayout class='monospaced'>
74 $ cd poky
75 $ git checkout -b 1.1 origin/1.1
76 Switched to a new branch '1.1'
77 </literallayout>
44 </para> 78 </para>
45 79 </section>
80
81 <section id='getting-a-local-copy-of-the-kernel-files'>
82 <title>Getting a Local Copy of the Kernel Files</title>
83
46 <para> 84 <para>
47 A big advantage to this scheme is the sharing of common features by keeping them in 85 You need to have a local copy of the Linux Yocto kernel files on your system.
48 "larger" branches that are further up the tree. 86 Yocto Project files available on your host system.
49 This practice eliminates redundant storage of similar features shared among kernels. 87 You must create a local Git repository of these files.
88 See the bulleted item
89 <link linkend='local-kernel-files'>Linux Yocto Kernel</link> in
90 <xref linkend='getting-setup'>Getting Setup</xref> earlier in this manual
91 for information on how to get these files.
50 </para> 92 </para>
93 </section>
94
95 <section id='create-a-layer-for-your-kernel-work'>
96 <title>Create a Layer for Your Kernel Work</title>
51 97
52 <para> 98 <para>
53 When you build the kernel on your development system all files needed for the build 99 It is always good to isolate your work using your own layer.
54 are taken from the Yocto Project source repositories pointed to by the 100 Doing so allows you to experiment and easily start over should things go wrong.
55 <filename>SRC_URI</filename> variable and gathered in a temporary work area 101 This example uses a layer named <filename>meta-vfatsupport</filename>.
56 where they are subsequently used to create the unique kernel.
57 Thus, in a sense, the process constructs a local source tree specific to your
58 kernel to generate the new kernel image - a source generator if you will.
59 </para> 102 </para>
60 103
61 <para> 104 <para>
62 For a complete discussion of the Yocto Project kernel's architcture and its branching strategy, 105 When you set up a layer for kernel work you should follow general layout
63 see the <ulink url='http://www.yoctoproject.org/docs/1.1/kernel-manual/kernel-manual.html'> 106 guidelines layers.
64 The Yocto Project Kernel Architecture and Use Manual</ulink>. 107 For example, if you were creating a BSP you would want to follow the layout
108 described in the
109 <ulink url='http://www.yoctoproject.org/docs/1.1/bsp-guide/bsp-guide.html#bsp-filelayout'>
110 Example Filesystem Layout</ulink> section of the Board Support Package (BSP) Development
111 Guide.
112 For kernel layers, you can start with a skeleton layer
113 named <filename>meta-skeleton</filename> found in your local
114 Yocto Project file directory structure (the <filename>poky</filename> Git
115 repository or the directory structure resulting from unpacking the Yocto Project
116 release tarball).
65 </para> 117 </para>
66 118
67 <para> 119 <para>
68 You can find a web interface to the Yocto Project source repository at 120 To create your kernel layer simply copy the <filename>meta-skeleton</filename>
69 <ulink url='http://git.yoctoproject.org/'></ulink>. 121 layer and rename it <filename>meta-vfatsupport</filename>.
70 Within the interface you will see groups of related source code, each of which can 122 The following command sets up the layer inside the <filename>poky</filename>
71 be cloned using Git to result in a working Git repository on your local system 123 Git repository:
72 (referred to as the "local Yocto Project files" in this manual). 124 <literallayout class='monospaced'>
73 The Yocto Project supports four types of kernels in its source repositories at 125 $ cd ~/poky
74 <ulink url='http://git.yoctoproject.org/'></ulink>: 126 $ cp -r meta-skeleton meta-vfatsupport
75 <itemizedlist> 127 </literallayout>
76 <listitem><para><emphasis><filename>linux-yocto-2.6.34</filename></emphasis> - The
77 stable Linux Yocto kernel that is based on the Linux 2.6.34 release.</para></listitem>
78 <listitem><para><emphasis><filename>linux-yocto-2.6.37</filename></emphasis> - The current
79 Linux Yocto kernel that is based on the Linux 2.6.37 release.</para></listitem>
80 <listitem><para><emphasis><filename>linux-yocto-dev</filename></emphasis> - A development
81 kernel based on the Linux 2.6.39-rc1 release.</para></listitem>
82 <listitem><para><emphasis><filename>linux-2.6</filename></emphasis> - A kernel based on
83 minimal Linux mainline tracking.
84 [WRITER'S NOTE: I don't know which Git repository the user needs to clone to get this
85 repository on their development system.]</para></listitem>
86 </itemizedlist>
87 </para> 128 </para>
88 </section>
89 129
90 <section id='modifying-a-kernel-example'> 130 <para>
91 <title>Modifying a Kernel Example</title> 131 In the new layer you will find areas for configuration changes
132 (<filename>conf</filename>) and recipe changes (<filename>recipes-skeleton</filename>).
133 </para>
92 134
93 <para> 135 <para>
94 This section presents a simple example that illustrates kernel modification 136 You need to modify the structure a bit for your work.
95 based on the <filename>linux-yocto-2.6.37</filename> kernel. 137 These commands add some further structure and names that the Yocto Project build
96 The example uses the audio and mixer capabilities supported by the 138 environment expect:
97 <ulink url='http://www.alsa-project.org/main/index.php/Main_Page'>Advanced Linux 139 <literallayout class='monospaced'>
98 Sound Architecture (ALSA) Project</ulink>. 140 $ mkdir meta-vfatsupport/images
99 As the example progresses you will see how to do the following: 141 $ mkdir meta-vfatsupport/recipes-bsp
100 <itemizedlist> 142 $ mv meta-vfatsupport/recipes-skeleton meta-vfatsupport/recipes-kernel
101 <listitem><para>Iteratively modify a base kernel locally.</para></listitem> 143 $ mkdir meta-vfatsupport/recipes-kernel/linux
102 <listitem><para>Provide a recipe-based solution for your modified kernel. 144 $ mkdir meta-vfatsupport/recipes-kernel/linux/linux-yocto
103 </para></listitem> 145 </literallayout>
104 <listitem><para>Proved an "in-tree" solution for your modified kernel
105 (i.e. make the modifcations part of the Yocto Project).</para></listitem>
106 </itemizedlist>
107 </para> 146 </para>
108 147
109 <para> 148 <para>
110 The example flows as follows: 149 The last piece you need for your layer is a
150 <filename>linux-yocto_git.bbappend</filename> file inside
151 <filename>meta-vfatsupport/recipes-kernel/linux</filename>.
152 This file needs the following content to make the build process aware of the
153 new layer's location:
154 <literallayout class='monospaced'>
155 FILESEXTRAPATHS := "${THISDIR}/${PN}"
156 </literallayout>
111 </para> 157 </para>
112 158
113 <para> 159 <para>
114 <itemizedlist> 160 [WRITER'S NOTE: We need a better <filename>meta-skeleton</filename> layer
115 <listitem><para>Be sure your host development system is set up to support 161 that is part of <filename>poky</filename>.
116 development using the Yocto Project. 162 It should have a structure that includes <filename>images</filename>,
117 See 163 <filename>recipes-bsp</filename>, <filename>recipes-kernel</filename>, and
118 <ulink url='http://www.yoctoproject.org/docs/1.1/yocto-project-qs/yocto-project-qs.html#the-linux-distro'> 164 so forth.
119 The Linux Distributions</ulink> section and 165 For now this step of the example is brute-forcing the structure with shell
120 <ulink url='http://www.yoctoproject.org/docs/1.1/yocto-project-qs/yocto-project-qs.html#packages'> 166 commands to set up the minimum structure and include the
121 The Packages</ulink> section both 167 <filename>.bbappend</filename> file.
122 in the Yocto Project Quick Start for requirements.
123 You will also need a release of Yocto Project installed on the host.</para></listitem>
124 <listitem><para>Set up your environment for optimal local kernel development.
125 </para></listitem>
126 <listitem><para>Create a layer to isolate your kernel work.</para></listitem>
127 <listitem><para>Next item.</para></listitem>
128 <listitem><para>Next item.</para></listitem>
129 <listitem><para>Next item.</para></listitem>
130 <listitem><para>Next item.</para></listitem>
131 </itemizedlist>
132 </para> 168 </para>
169 </section>
133 170
134 <section id='setting-up-yocto-project-kernel-example'> 171 <section id='prepare-to-use-menuconfig'>
135 <title>Setting Up Yocto Project</title> 172 <title>Prepare to use <filename>menuconfig</filename></title>
173
174 <para>
175 The <filename>menuconfig</filename> tool provides an interactive method with which
176 to set kernel configurations.
177 In order to use <filename>menuconfig</filename> from within the BitBake environment
178 you need to source an environment setup script.
179 This script is located in the local Yocto Project file structure and is called
180 <filename>oe-init-build-env</filename>.
181 </para>
136 182
137 <para> 183 <para>
138 You need to have the Yocto Project files available on your host system. 184 The following command sets up the environment:
139 The process is identical to that described in the 185 <literallayout class='monospaced'>
140 <xref linkend='getting-setup'>"Getting Setup"</xref> section earlier in this 186 $ cd ~/poky
141 manual. 187 $ source oe-init-build-env
142 Be sure to either set up a local Git repository for <filename>poky</filename> 188 </literallayout>
143 or download and unpack the Yocto Project release tarball. 189 </para>
144 </para> 190 </section>
145 </section>
146 191
147 <section id='create-a-git-repository-of-poky-extras'> 192 <section id='make-configuration-changes-to-the-kernel'>
148 <title>Create a Git Repository of <filename>poky-extras</filename></title> 193 <title>Make Configuration Changes to the Kernel</title>
194
195 <para>
196 After setting up the environment to run <filename>menuconfig</filename> you are ready
197 to use the tool to interactively change the kernel configuration.
198 In this example we are basing our changes on the <filename>linux-yocto-2.6.37</filename>
199 kernel.
200 The Yocto Project build environment recognizes this kernel as
201 <filename>linux-yocto</filename>.
202 Thus, the following command from the shell in which you previously sourced the
203 environment initialization script launches <filename>menuconfig</filename>:
204 <literallayout class='monospaced'>
205 $ bitbake linux-yocto -c menuconfig
206 </literallayout>
207 </para>
149 208
150 <para> 209 <para>
151 Everytime you change a configuration or add a recipe to the kernel you need to 210 [WRITER'S NOTE: Stuff from here down are crib notes]
152 do a fetch from the Linux Yocto kernel source repositories. 211 </para>
153 This can get tedious and time consuming if you need to fetch the entire
154 Linux Yocto 2.6.37 Git repository down from the Internet everytime you make a change
155 to the kernel.
156 </para>
157 212
158 <para> 213 <para>
159 You can get around this by setting up a <filename>meta-kernel-dev</filename> 214 Once menuconfig fires up you see all kinds of categories that you can interactively
160 area on your local system. 215 investigate.
161 This area contains "append" files for every kernel recipe, which also include 216 If they have an "M" in it then the feature is "modularized".
162 a <filename>KSRC</filename> statement that points to the kernel source files. 217 I guess that means that means that it needs to be manually linked in when the
163 You can set up the environment so that the <filename>KSRC</filename> points to the 218 kernel is booted??? (Not sure).
164 <filename>meta-kernel-dev</filename>, thus pulling source from a local area. 219 If they have an "*" then the feature is automatically part of the kernel.]
165 This setup can speed up development time. 220 </para>
166 </para>
167
168 <para>
169 To get set up you need to do two things: create a local Git repository
170 of the <filename>poky-extras</filename> repository, and create a bare clone of the
171 Linux Yocto 2.6.37 kernel Git repository.
172 </para>
173
174 <para>
175 The following transcript shows how to clone the <filename>poky-extras</filename>
176 Git repository into the current working directory, which is <filename>poky</filename>
177 in this example.
178 The command creates the repository in a directory named <filename>poky-extras</filename>:
179 <literallayout class='monospaced'>
180 $ git clone git://git.yoctoproject.org/poky-extras
181 Initialized empty Git repository in /home/scottrif/poky/poky-extras/.git/
182 remote: Counting objects: 532, done.
183 remote: Compressing objects: 100% (472/472), done.
184 remote: Total 532 (delta 138), reused 307 (delta 39)
185 Receiving objects: 100% (532/532), 534.28 KiB | 362 KiB/s, done.
186 Resolving deltas: 100% (138/138), done.
187 </literallayout>
188 </para>
189 221
190 <para> 222 <para>
191 This transcript shows how to clone a bare Git repository of the Linux Yocto 223 So the tmp/work/ area was created in poky and there is a .config file in there and
192 2.6.37 kernel: 224 a .config.old file.
193 <literallayout class='monospaced'> 225 The old one must have been created when I exited from menuconfig after poking around
194 $ git clone --bare git://git.yoctoproject.org/linux-yocto-2.6.37 226 a bit.
195 Initialized empty Git repository in /home/scottrif/linux-yocto-2.6.37.git/ 227 Nope - appears to just be created automatically.
196 remote: Counting objects: 1886034, done. 228 </para>
197 remote: Compressing objects: 100% (314326/314326), done.
198 remote: Total 1886034 (delta 1570202), reused 1870335 (delta 1554798)
199 Receiving objects: 100% (1886034/1886034), 401.51 MiB | 714 KiB/s, done.
200 Resolving deltas: 100% (1570202/1570202), done.
201 </literallayout>
202 </para>
203 229
204 <para> 230 <para>
205 The bare clone of the Linux Yocto 2.6.37 kernel on your local system mirrors 231 A good practice is to first determine what configurations you have for the kernel.
206 the upstream repository of the kernel. 232 You can see the results by looking in the .config file in the build/tmp/work/qemux86-poky-linux area
207 You can effectively point to this local clone now during development to avoid 233 of the local YP files.
208 having to fetch the entire Linux Yocto 2.6.37 kernel every time you make a 234 There is a directory named linux-yocto-2.6.37* in the directory.
209 kernel change. 235 In that directory is a directory named linux-qemux86-standard-build.
210 </para> 236 In that directory you will find a file named .config that is the configuration file
211 </section> 237 for the kernel that will be used when you build the kernel.
238 You can open that file up and examine it.
239 If you do a search for "VFAT" you will see that that particular configuration is not
240 enabled for the kernel.
241 This means that you cannot print a VFAT text file, or for that matter, even mount one
242 from the image if you were to build it at this point.
243 </para>
212 244
213 <section id='create-a-layer-for-your-kernel-work'> 245 <para>
214 <title>Create a Layer for Your Kernel Work</title> 246 You can prove the point by actually trying it at this point.
247 Here are the commands:
248 <literallayout class='monospaced'>
249 $ mkdir ~/vfat-test
250 $ cd ~/vfat-test
251 $ dd if=/dev/zero of=vfat.img bs=1024 count=5000 [creates a 5MB disk image]
252 5+0 records in
253 5+0 records out
254 5242880 bytes (5.2 MB) copied, 0.00798912 s, 656 MB/s
255 $ ls -lah [lists the contents of the new image. l=long, a=all, h=human readable]
256 total 5.1M
257 drwxr-xr-x 2 srifenbark scottrif 4.0K 2011-08-01 08:18 .
258 drwxr-xr-x 66 srifenbark scottrif 4.0K 2011-08-01 08:14 ..
259 -rw-r--r-- 1 srifenbark scottrif 5.0M 2011-08-01 08:18 vfat.img
260 $ mkfs.vfat vfat.img [formats the disk image]
261 mkfs.vfat 3.0.7 (24 Dec 2009)
262 $ mkdir mnt [mounts the disk image]
263 $ sudo su [gives you root privilege]
264 # mount -o loop vfat.img mnt [mounts it as a loop device]
265 # ls mnt [shows nothing in mnt]
266 # mount [lists the mounted filesystems - note/dev/loop0]
267 /dev/sda1 on / type ext4 (rw,errors=remount-ro)
268 proc on /proc type proc (rw,noexec,nosuid,nodev)
269 none on /sys type sysfs (rw,noexec,nosuid,nodev)
270 none on /sys/fs/fuse/connections type fusectl (rw)
271 none on /sys/kernel/debug type debugfs (rw)
272 none on /sys/kernel/security type securityfs (rw)
273 none on /dev type devtmpfs (rw,mode=0755)
274 none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
275 none on /dev/shm type tmpfs (rw,nosuid,nodev)
276 none on /var/run type tmpfs (rw,nosuid,mode=0755)
277 none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
278 none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
279 binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
280 gvfs-fuse-daemon on /home/scottrif/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=srifenbark)
281 /dev/loop0 on /home/scottrif/vfat-test/mnt type vfat (rw)
282 # echo "hello world" > mnt/hello.txt [creates a text file in the mounted VFAT system]
283 # ls mnt [verifies the file is there]
284 hello.txt
285 # cat mnt/hello.txt [displays the contents of the file created]
286 hello world
287 # umount mnt [unmounts the system and destroys the loop]
288 # exit [gets out of privileged user mode]
289 exit
290
291 $ lsmod [this stuff Darren did to show me ]
292 Module Size Used by [the status of modules in the regular linux kernel]
293 nls_iso8859_1 4633 0
294 nls_cp437 6351 0
295 vfat 10866 0
296 fat 55350 1 vfat
297 snd_hda_codec_atihdmi 3023 1
298 binfmt_misc 7960 1
299 snd_hda_codec_realtek 279008 1
300 ppdev 6375 0
301 snd_hda_intel 25805 2
302 fbcon 39270 71
303 tileblit 2487 1 fbcon
304 font 8053 1 fbcon
305 bitblit 5811 1 fbcon
306 snd_hda_codec 85759 3 snd_hda_codec_atihdmi,snd_hda_codec_realtek,snd_hda_intel
307 softcursor 1565 1 bitblit
308 snd_seq_dummy 1782 0
309 snd_hwdep 6924 1 snd_hda_codec
310 vga16fb 12757 0
311 snd_pcm_oss 41394 0
312 snd_mixer_oss 16299 1 snd_pcm_oss
313 snd_pcm 87946 3 snd_hda_intel,snd_hda_codec,snd_pcm_oss
314 vgastate 9857 1 vga16fb
315 snd_seq_oss 31191 0
316 snd_seq_midi 5829 0
317 snd_rawmidi 23420 1 snd_seq_midi
318 radeon 744506 3
319 snd_seq_midi_event 7267 2 snd_seq_oss,snd_seq_midi
320 ttm 61007 1 radeon
321 snd_seq 57481 6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event
322 drm_kms_helper 30742 1 radeon
323 snd_timer 23649 2 snd_pcm,snd_seq
324 snd_seq_device 6888 5 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_rawmidi,snd_seq
325 usb_storage 50377 0
326 snd 71283 16 \
327 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec, \
328 snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm, \
329 snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
330 soundcore 8052 1 snd
331 psmouse 65040 0
332 drm 198886 5 radeon,ttm,drm_kms_helper
333 i2c_algo_bit 6024 1 radeon
334 serio_raw 4918 0
335 snd_page_alloc 8500 2 snd_hda_intel,snd_pcm
336 dell_wmi 2177 0
337 dcdbas 6886 0
338 lp 9336 0
339 parport 37160 2 ppdev,lp
340 usbhid 41116 0
341 ohci1394 30260 0
342 hid 83888 1 usbhid
343 ieee1394 94771 1 ohci1394
344 tg3 122382 0
345 </literallayout>
346 </para>
347 </section>
348 </section>
349</appendix>
215 350
216 <para>
217 It is always good to isolate your work using your own layer.
218 Doing so allows you to experiment and easily start over should things go wrong.
219 This example uses a layer named <filename>meta-amixer</filename>.
220 </para>
221 351
222 <para> 352<!--
223 When you set up a layer for kernel work you should follow the general layout
224 guidelines as described for BSP layers.
225 This layout is described in the
226 <ulink url='http://www.yoctoproject.org/docs/1.1/bsp-guide/bsp-guide.html#bsp-filelayout'>
227 Example Filesystem Layout</ulink> section of the Board Support Package (BSP) Development
228 Guide.
229 In the standard layout you will notice a suggested structure for recipes and
230 configuration information.
231 [WRITER'S NOTE: The <filename>meta-elc</filename> example uses an
232 <filename>images</filename> directory.
233 Currently, <filename>images</filename> is not part of the standard BSP layout.
234 I need to find out from Darren if this directory is required for kernel work.]
235 </para>
236 353
237 <para> 354EXTRA STUFF I MIGHT NEED BUT NOW SURE RIGHT NOW.
238 [WRITER'S NOTE: I need a paragraph here describing how to set up the layer.
239 I am not sure if you should copy an existing BSP layer and modify from there.
240 Or, if you should just look at a BSP layer and then create your own files.
241 Email to Darren on this but no answer yet.]
242 </para>
243 </section>
244 355
245 <section id='making-changes-to-your-kernel-layer'> 356In the standard layer structure you have several areas that you need to examine or
246 <title>Making Changes to Your Kernel Layer</title>
247
248 <para>
249 In the standard layer structure you have several areas that you need to examine or
250 modify. 357 modify.
251 For this example the layer contains four areas: 358 For this example the layer contains four areas:
252 <itemizedlist> 359 <itemizedlist>
@@ -375,10 +482,8 @@
375 The file can also contain <filename>KERNEL_FEATURES</filename> statements that specify 482 The file can also contain <filename>KERNEL_FEATURES</filename> statements that specify
376 included kernel configurations that ship with the Yocto Project. 483 included kernel configurations that ship with the Yocto Project.
377 </para> 484 </para>
378 </section> 485-->
379 </section>
380 486
381</appendix>
382<!-- 487<!--
383vim: expandtab tw=80 ts=4 488vim: expandtab tw=80 ts=4
384--> 489-->
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