drivers: power: report battery voltage in AOSP compatible format
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / README
1 Linux kernel release 3.x <>
3 These are the release notes for Linux version 3. Read them carefully,
4 as they tell you what this is all about, explain how to install the
5 kernel, and what to do if something goes wrong.
9 Linux is a clone of the operating system Unix, written from scratch by
10 Linus Torvalds with assistance from a loosely-knit team of hackers across
11 the Net. It aims towards POSIX and Single UNIX Specification compliance.
13 It has all the features you would expect in a modern fully-fledged Unix,
14 including true multitasking, virtual memory, shared libraries, demand
15 loading, shared copy-on-write executables, proper memory management,
16 and multistack networking including IPv4 and IPv6.
18 It is distributed under the GNU General Public License - see the
19 accompanying COPYING file for more details.
23 Although originally developed first for 32-bit x86-based PCs (386 or higher),
24 today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
25 UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
26 IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS,
27 Xtensa, Tilera TILE, AVR32 and Renesas M32R architectures.
29 Linux is easily portable to most general-purpose 32- or 64-bit architectures
30 as long as they have a paged memory management unit (PMMU) and a port of the
31 GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
32 also been ported to a number of architectures without a PMMU, although
33 functionality is then obviously somewhat limited.
34 Linux has also been ported to itself. You can now run the kernel as a
35 userspace application - this is called UserMode Linux (UML).
39 - There is a lot of documentation available both in electronic form on
40 the Internet and in books, both Linux-specific and pertaining to
41 general UNIX questions. I'd recommend looking into the documentation
42 subdirectories on any Linux FTP site for the LDP (Linux Documentation
43 Project) books. This README is not meant to be documentation on the
44 system: there are much better sources available.
46 - There are various README files in the Documentation/ subdirectory:
47 these typically contain kernel-specific installation notes for some
48 drivers for example. See Documentation/00-INDEX for a list of what
49 is contained in each file. Please read the Changes file, as it
50 contains information about the problems, which may result by upgrading
51 your kernel.
53 - The Documentation/DocBook/ subdirectory contains several guides for
54 kernel developers and users. These guides can be rendered in a
55 number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.
56 After installation, "make psdocs", "make pdfdocs", "make htmldocs",
57 or "make mandocs" will render the documentation in the requested format.
59 INSTALLING the kernel source:
61 - If you install the full sources, put the kernel tarball in a
62 directory where you have permissions (eg. your home directory) and
63 unpack it:
65 gzip -cd linux-3.X.tar.gz | tar xvf -
67 or
69 bzip2 -dc linux-3.X.tar.bz2 | tar xvf -
71 Replace "X" with the version number of the latest kernel.
73 Do NOT use the /usr/src/linux area! This area has a (usually
74 incomplete) set of kernel headers that are used by the library header
75 files. They should match the library, and not get messed up by
76 whatever the kernel-du-jour happens to be.
78 - You can also upgrade between 3.x releases by patching. Patches are
79 distributed in the traditional gzip and the newer bzip2 format. To
80 install by patching, get all the newer patch files, enter the
81 top level directory of the kernel source (linux-3.X) and execute:
83 gzip -cd ../patch-3.x.gz | patch -p1
85 or
87 bzip2 -dc ../patch-3.x.bz2 | patch -p1
89 Replace "x" for all versions bigger than the version "X" of your current
90 source tree, _in_order_, and you should be ok. You may want to remove
91 the backup files (some-file-name~ or some-file-name.orig), and make sure
92 that there are no failed patches (some-file-name# or some-file-name.rej).
93 If there are, either you or I have made a mistake.
95 Unlike patches for the 3.x kernels, patches for the 3.x.y kernels
96 (also known as the -stable kernels) are not incremental but instead apply
97 directly to the base 3.x kernel. For example, if your base kernel is 3.0
98 and you want to apply the 3.0.3 patch, you must not first apply the 3.0.1
99 and 3.0.2 patches. Similarly, if you are running kernel version 3.0.2 and
100 want to jump to 3.0.3, you must first reverse the 3.0.2 patch (that is,
101 patch -R) _before_ applying the 3.0.3 patch. You can read more on this in
102 Documentation/applying-patches.txt
104 Alternatively, the script patch-kernel can be used to automate this
105 process. It determines the current kernel version and applies any
106 patches found.
108 linux/scripts/patch-kernel linux
110 The first argument in the command above is the location of the
111 kernel source. Patches are applied from the current directory, but
112 an alternative directory can be specified as the second argument.
114 - Make sure you have no stale .o files and dependencies lying around:
116 cd linux
117 make mrproper
119 You should now have the sources correctly installed.
123 Compiling and running the 3.x kernels requires up-to-date
124 versions of various software packages. Consult
125 Documentation/Changes for the minimum version numbers required
126 and how to get updates for these packages. Beware that using
127 excessively old versions of these packages can cause indirect
128 errors that are very difficult to track down, so don't assume that
129 you can just update packages when obvious problems arise during
130 build or operation.
132 BUILD directory for the kernel:
134 When compiling the kernel, all output files will per default be
135 stored together with the kernel source code.
136 Using the option "make O=output/dir" allow you to specify an alternate
137 place for the output files (including .config).
138 Example:
140 kernel source code: /usr/src/linux-3.X
141 build directory: /home/name/build/kernel
143 To configure and build the kernel, use:
145 cd /usr/src/linux-3.X
146 make O=/home/name/build/kernel menuconfig
147 make O=/home/name/build/kernel
148 sudo make O=/home/name/build/kernel modules_install install
150 Please note: If the 'O=output/dir' option is used, then it must be
151 used for all invocations of make.
153 CONFIGURING the kernel:
155 Do not skip this step even if you are only upgrading one minor
156 version. New configuration options are added in each release, and
157 odd problems will turn up if the configuration files are not set up
158 as expected. If you want to carry your existing configuration to a
159 new version with minimal work, use "make oldconfig", which will
160 only ask you for the answers to new questions.
162 - Alternative configuration commands are:
164 "make config" Plain text interface.
166 "make menuconfig" Text based color menus, radiolists & dialogs.
168 "make nconfig" Enhanced text based color menus.
170 "make xconfig" X windows (Qt) based configuration tool.
172 "make gconfig" X windows (Gtk) based configuration tool.
174 "make oldconfig" Default all questions based on the contents of
175 your existing ./.config file and asking about
176 new config symbols.
178 "make silentoldconfig"
179 Like above, but avoids cluttering the screen
180 with questions already answered.
181 Additionally updates the dependencies.
183 "make olddefconfig"
184 Like above, but sets new symbols to their default
185 values without prompting.
187 "make defconfig" Create a ./.config file by using the default
188 symbol values from either arch/$ARCH/defconfig
189 or arch/$ARCH/configs/${PLATFORM}_defconfig,
190 depending on the architecture.
192 "make ${PLATFORM}_defconfig"
193 Create a ./.config file by using the default
194 symbol values from
195 arch/$ARCH/configs/${PLATFORM}_defconfig.
196 Use "make help" to get a list of all available
197 platforms of your architecture.
199 "make allyesconfig"
200 Create a ./.config file by setting symbol
201 values to 'y' as much as possible.
203 "make allmodconfig"
204 Create a ./.config file by setting symbol
205 values to 'm' as much as possible.
207 "make allnoconfig" Create a ./.config file by setting symbol
208 values to 'n' as much as possible.
210 "make randconfig" Create a ./.config file by setting symbol
211 values to random values.
213 "make localmodconfig" Create a config based on current config and
214 loaded modules (lsmod). Disables any module
215 option that is not needed for the loaded modules.
217 To create a localmodconfig for another machine,
218 store the lsmod of that machine into a file
219 and pass it in as a LSMOD parameter.
221 target$ lsmod > /tmp/mylsmod
222 target$ scp /tmp/mylsmod host:/tmp
224 host$ make LSMOD=/tmp/mylsmod localmodconfig
226 The above also works when cross compiling.
228 "make localyesconfig" Similar to localmodconfig, except it will convert
229 all module options to built in (=y) options.
231 You can find more information on using the Linux kernel config tools
232 in Documentation/kbuild/kconfig.txt.
234 - NOTES on "make config":
236 - Having unnecessary drivers will make the kernel bigger, and can
237 under some circumstances lead to problems: probing for a
238 nonexistent controller card may confuse your other controllers
240 - Compiling the kernel with "Processor type" set higher than 386
241 will result in a kernel that does NOT work on a 386. The
242 kernel will detect this on bootup, and give up.
244 - A kernel with math-emulation compiled in will still use the
245 coprocessor if one is present: the math emulation will just
246 never get used in that case. The kernel will be slightly larger,
247 but will work on different machines regardless of whether they
248 have a math coprocessor or not.
250 - The "kernel hacking" configuration details usually result in a
251 bigger or slower kernel (or both), and can even make the kernel
252 less stable by configuring some routines to actively try to
253 break bad code to find kernel problems (kmalloc()). Thus you
254 should probably answer 'n' to the questions for "development",
255 "experimental", or "debugging" features.
257 COMPILING the kernel:
259 - Make sure you have at least gcc 3.2 available.
260 For more information, refer to Documentation/Changes.
262 Please note that you can still run a.out user programs with this kernel.
264 - Do a "make" to create a compressed kernel image. It is also
265 possible to do "make install" if you have lilo installed to suit the
266 kernel makefiles, but you may want to check your particular lilo setup first.
268 To do the actual install, you have to be root, but none of the normal
269 build should require that. Don't take the name of root in vain.
271 - If you configured any of the parts of the kernel as `modules', you
272 will also have to do "make modules_install".
274 - Verbose kernel compile/build output:
276 Normally, the kernel build system runs in a fairly quiet mode (but not
277 totally silent). However, sometimes you or other kernel developers need
278 to see compile, link, or other commands exactly as they are executed.
279 For this, use "verbose" build mode. This is done by inserting
280 "V=1" in the "make" command. E.g.:
282 make V=1 all
284 To have the build system also tell the reason for the rebuild of each
285 target, use "V=2". The default is "V=0".
287 - Keep a backup kernel handy in case something goes wrong. This is
288 especially true for the development releases, since each new release
289 contains new code which has not been debugged. Make sure you keep a
290 backup of the modules corresponding to that kernel, as well. If you
291 are installing a new kernel with the same version number as your
292 working kernel, make a backup of your modules directory before you
293 do a "make modules_install".
295 Alternatively, before compiling, use the kernel config option
296 "LOCALVERSION" to append a unique suffix to the regular kernel version.
297 LOCALVERSION can be set in the "General Setup" menu.
299 - In order to boot your new kernel, you'll need to copy the kernel
300 image (e.g. .../linux/arch/i386/boot/bzImage after compilation)
301 to the place where your regular bootable kernel is found.
303 - Booting a kernel directly from a floppy without the assistance of a
304 bootloader such as LILO, is no longer supported.
306 If you boot Linux from the hard drive, chances are you use LILO, which
307 uses the kernel image as specified in the file /etc/lilo.conf. The
308 kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
309 /boot/bzImage. To use the new kernel, save a copy of the old image
310 and copy the new image over the old one. Then, you MUST RERUN LILO
311 to update the loading map!! If you don't, you won't be able to boot
312 the new kernel image.
314 Reinstalling LILO is usually a matter of running /sbin/lilo.
315 You may wish to edit /etc/lilo.conf to specify an entry for your
316 old kernel image (say, /vmlinux.old) in case the new one does not
317 work. See the LILO docs for more information.
319 After reinstalling LILO, you should be all set. Shutdown the system,
320 reboot, and enjoy!
322 If you ever need to change the default root device, video mode,
323 ramdisk size, etc. in the kernel image, use the 'rdev' program (or
324 alternatively the LILO boot options when appropriate). No need to
325 recompile the kernel to change these parameters.
327 - Reboot with the new kernel and enjoy.
331 - If you have problems that seem to be due to kernel bugs, please check
332 the file MAINTAINERS to see if there is a particular person associated
333 with the part of the kernel that you are having trouble with. If there
334 isn't anyone listed there, then the second best thing is to mail
335 them to me (, and possibly to any other
336 relevant mailing-list or to the newsgroup.
338 - In all bug-reports, *please* tell what kernel you are talking about,
339 how to duplicate the problem, and what your setup is (use your common
340 sense). If the problem is new, tell me so, and if the problem is
341 old, please try to tell me when you first noticed it.
343 - If the bug results in a message like
345 unable to handle kernel paging request at address C0000010
346 Oops: 0002
347 EIP: 0010:XXXXXXXX
348 eax: xxxxxxxx ebx: xxxxxxxx ecx: xxxxxxxx edx: xxxxxxxx
349 esi: xxxxxxxx edi: xxxxxxxx ebp: xxxxxxxx
350 ds: xxxx es: xxxx fs: xxxx gs: xxxx
351 Pid: xx, process nr: xx
352 xx xx xx xx xx xx xx xx xx xx
354 or similar kernel debugging information on your screen or in your
355 system log, please duplicate it *exactly*. The dump may look
356 incomprehensible to you, but it does contain information that may
357 help debugging the problem. The text above the dump is also
358 important: it tells something about why the kernel dumped code (in
359 the above example, it's due to a bad kernel pointer). More information
360 on making sense of the dump is in Documentation/oops-tracing.txt
362 - If you compiled the kernel with CONFIG_KALLSYMS you can send the dump
363 as is, otherwise you will have to use the "ksymoops" program to make
364 sense of the dump (but compiling with CONFIG_KALLSYMS is usually preferred).
365 This utility can be downloaded from
366 ftp://ftp.<country> .
367 Alternatively, you can do the dump lookup by hand:
369 - In debugging dumps like the above, it helps enormously if you can
370 look up what the EIP value means. The hex value as such doesn't help
371 me or anybody else very much: it will depend on your particular
372 kernel setup. What you should do is take the hex value from the EIP
373 line (ignore the "0010:"), and look it up in the kernel namelist to
374 see which kernel function contains the offending address.
376 To find out the kernel function name, you'll need to find the system
377 binary associated with the kernel that exhibited the symptom. This is
378 the file 'linux/vmlinux'. To extract the namelist and match it against
379 the EIP from the kernel crash, do:
381 nm vmlinux | sort | less
383 This will give you a list of kernel addresses sorted in ascending
384 order, from which it is simple to find the function that contains the
385 offending address. Note that the address given by the kernel
386 debugging messages will not necessarily match exactly with the
387 function addresses (in fact, that is very unlikely), so you can't
388 just 'grep' the list: the list will, however, give you the starting
389 point of each kernel function, so by looking for the function that
390 has a starting address lower than the one you are searching for but
391 is followed by a function with a higher address you will find the one
392 you want. In fact, it may be a good idea to include a bit of
393 "context" in your problem report, giving a few lines around the
394 interesting one.
396 If you for some reason cannot do the above (you have a pre-compiled
397 kernel image or similar), telling me as much about your setup as
398 possible will help. Please read the REPORTING-BUGS document for details.
400 - Alternatively, you can use gdb on a running kernel. (read-only; i.e. you
401 cannot change values or set break points.) To do this, first compile the
402 kernel with -g; edit arch/i386/Makefile appropriately, then do a "make
403 clean". You'll also need to enable CONFIG_PROC_FS (via "make config").
405 After you've rebooted with the new kernel, do "gdb vmlinux /proc/kcore".
406 You can now use all the usual gdb commands. The command to look up the
407 point where your system crashed is "l *0xXXXXXXXX". (Replace the XXXes
408 with the EIP value.)
410 gdb'ing a non-running kernel currently fails because gdb (wrongly)
411 disregards the starting offset for which the kernel is compiled.