ESP8266 Community Forum

- Sun Aug 31, 2014 2:17 pm #69 @jonsmirl

Nice to see you here

- Sun Aug 31, 2014 4:03 pm #71

Seems like we have the overlay readily available? (although we are, again legally, likely unable to really use it if anyone is watching us ).

IANAL, but ALL source header files within the overlay file are either GPLv2 or higher, or this rather permissive license:

Code: Select all  Copyright (c) 1999-2010 Tensilica Inc.

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   "Software"), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be included
   in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


So way may be able to use the overlay without legal restrictions, after all!

- Sun Aug 31, 2014 4:10 pm #72 The overlay files contain the following "gcc/README" file, explaining how to compile GCC instead of using the compielr provided by Tensilica:

Code: Select allREADME for GCC Source Files
------------------------------------------------------------------------

If for some reason you prefer to use GCC instead of the compiler provided
by Tensilica, you can obtain the standard GCC source files and build an
Xtensa cross compiler.

The Xtensa processor support is included in the standard GCC sources.
After obtaining the GCC source files, you only need to add your Xtensa
configuration information by copying the "xtensa-config.h" file in this
directory into the GCC source tree.  For GCC 3.4 and later versions, copy
this file into the "include" directory; for GCC 3.3 and earlier versions,
copy it into the "gcc/config/xtensa" directory.  You can then follow the
standard directions for building and installing a GCC cross compiler.

Please refer to the installation instructions included with GCC for
detailed directions.  (The instructions for the latest version of GCC
are also available at http://gcc.gnu.org/install/.)  The following
steps illustrate one way to build GCC, assuming you are using the
binutils from Tensilica's Xtensa Tools.

The following directories are referenced in the build steps below:

     $gccsrc            top-level directory from the GCC source tar file
     $prefix            new directory where you will install GCC
     $xtensa_tools_root  root directory of Tensilica's Xtensa Tools
     $xtensa_root        root directory for your Xtensa configuration
     $build            new directory used temporarily for building GCC

We use shell variable syntax to refer to these directories.  You can
define the corresponding shell variables or you can just substitute
the appropriate directory names where they are referenced.

1. Obtain the GCC source tar file.  Extract the files to create the
$gccsrc directory.  Add your Xtensa configuration information by
copying a header file:

     cp $xtensa_root/src/gcc/xtensa-config.h $gccsrc/include

     or for GCC 3.3 and earlier versions:
     cp $xtensa_root/src/gcc/xtensa-config.h $gccsrc/gcc/config/xtensa

2. Create some of the directories where you want to install GCC.

     mkdir -p $prefix/bin $prefix/xtensa-elf
     (cd $prefix/xtensa-elf; mkdir arch bin include lib)

3. Add symbolic links to Xtensa Tools and Xtensa configuration files.
The following commands use Bourne shell (/bin/sh) syntax so you need
to either use a compatible shell or translate the commands to match
your shell.

     cd $prefix/bin
     for f in $xtensa_tools_root/bin/xt-*; do
       newf=`basename $f | sed -e s/xt-/xtensa-elf-/`
       rm -f $newf `basename $f`
       ln -s $f $newf
       ln -s $newf `basename $f`
     done

     cd $prefix/xtensa-elf/bin
     ln -s ../../bin/xtensa-elf-as as

     cd $prefix/xtensa-elf
     for d in arch include lib; do
       (cd $d; $gccsrc/symlink-tree $xtensa_root/xtensa-elf/$d)
       if [ -r $xtensa_tools_root/xtensa-elf/$d ]; then
         (cd $d; $gccsrc/symlink-tree $xtensa_tools_root/xtensa-elf/$d)
       fi
     done

4. Set up your environment.  Besides the PATH setting shown, be sure
to set XTENSA_CORE (and possibly XTENSA_SYSTEM) as needed to specify
the Xtensa configuration for which you are building GCC.

     PATH=$prefix/bin:$PATH

5. Create the $build directory and run the configure script.  The
$build directory should not be located inside either $prefix or
$gccsrc.

     mkdir $build
     cd $build
     $gccsrc/configure --target=xtensa-elf --prefix=$prefix \
       --enable-languages="c,c++" --disable-shared \
       --with-as=$prefix/bin/xtensa-elf-as \
       --with-ld=$prefix/bin/xtensa-elf-ld \
       --with-gxx-include-dir=$prefix/xtensa-elf/include/c++ \
       --with-newlib

6. Build and install GCC.

     cd $build
     make all install



I haven't try it yet, but it looks like it is all we need to get our own free GCC compiler!

Then all that is left to open this CPU are the binary library blobs in /lib ("xt-objdump -D" is your friend ) and find the way to inject our firmware in it.

- Mon Sep 01, 2014 1:08 am #77

IANAL, but ALL source header files within the overlay file are either GPLv2 or higher, or this rather permissive license: [...]

Yay! I should have read those headers instead of skipping them by default