This patch configures Isolated Memory Regions (IMRs) to block DMA to
code and data regions that do not contain any data that needs to be
DMA-accessible.
The Intel Quark X1000 SoC includes support for Isolated Memory Regions
(IMRs), which are specified using range registers and associated
control registers that are accessible via the message bus. This patch
adds a driver for accessing those registers.
The Intel Quark X1000 SoC includes a message bus that is accessible
via PCI configuration registers. It communicates to various SoC
components such as the Isolated Memory Region (IMR) registers and the
Remote Management Unit. This patch adds a driver for accessing the
message bus.
This patch revises the I2C and GPIO initialization code to always be
run during platform boot rather than within each process that requires
it.
This patch also revises the gpio-output example to use a pin that is
set as an output by the default pinmux configuration. Previously, it
used a pin that was set as an output by the pinmux configuration that
is in effect when the OS does not change the pinmux configuration.
This patch permits interrupts to be generated by both the I2C and GPIO
controllers for simultaneously-executing applications. The controllers
share a single interrupt pin, INTC. Prior to this patch,
quarkX1000_gpio_init() routed INTA to PIRQC and IRQ 10 (due to an
incorrect assumption that INTA is connected to the GPIO controller),
and quarkX1000_i2c_init() routed INTC to PIRQC and IRQ 9. The I2C
controller initialization is a prerequisite for GPIO initialization,
so the final configuration was that INTA and INTC were both routed to
PIRQC and IRQ 10. Thus, only the GPIO ISR was being invoked, even if
the I2C controller was actually responsible for the interrupt.
This patch refactors the I2C and GPIO ISR setup and handler code so
that the shared portions are combined in
cpu/x86/drivers/legacy_pc/shared-isr.[ch]. The I2C and GPIO drivers
communicate their interrupt information to the shared component by
placing structures in a specific section of the binary.
This commit creates a `common` directory, aimed to host drivers supported by multiple boards of the CC13xx/CC26xx family.
We move the Sensortag SPI and External Flash drivers to this location and we change the Sensortag build system to pull the respective files from therein.
The driver currently supports two Winbond external flash parts with identical instruction sets. The instruction set of the Macronix MX25R8035F appears to be a superset. We therefore change the driver to add the MID/DID of the Macronix to the list of supported parts.
This will subsequently allow us to share the same driver for both the SensorTag and the CC2650 LauchPad.
This patch revises the compiler flags when LLVM Clang is in use to
cause Clang to automatically use its built-in header files rather than
those for GCC.
Also added a 2-minutes average wind direction value, replaced the 240 bytes buffer from the reference example, but probably there's room for efficiency improvement
This is to prevent a compile error caused by function prototype conflict between a function called `select()` (present in a number of sensortag peripheral drivers) and the one in `sys/select.h`. The error manifests itself with gcc-arm-embedded version 5.2.1 20151202 (2015-q4).
To fix the error we simply rename our function.
Fixes#1434
This patch adds support for optionally building EFI binaries in
addition to Multiboot ELF binaries. It includes a script,
build_uefi.sh, that downloads tool and library sources from the EDK II
project, builds the GenFw tool that is used to create UEFI binaries,
and creates a makefile that is included from the main x86 common
makefile and enables UEFI support in the Contiki build system. If the
script is not run prior to building Contiki, then an informational
message will be displayed with instructions for running build_uefi.sh
if UEFI support is desired. This patch also adds the path to the
auto-generated makefile to .gitignore.
This patch modifies the linker script for the Intel Quark X1000 to
account for the output file section offsets and alignment expectations
of the EDK II GenFw project.
This patch also adds a newlib patch to remove the weak symbol
attribute from floating point stdio support routines. See
<newlib>/newlib/README for an explanation of how the newlib developers
intended for _printf_float and _scanf_float to be linked. Newlib
declares them as weak symbols with the intention that developers would
force them to be linked only when needed using a linker command line
option. However, some but not all Contiki programs require them, so
we cannot simply always include or exclude them. Instead, we remove
the weak symbol attributes and rely on the linker to automatically
determine whether or not they should be linked. This avoids an issue
in which weak symbols were undefined in the intermediate DLL generated
as part of the UEFI build process. That resulted in the GenFw program
emitting "ERROR 3000" messages when it encountered relocations
referencing such an undefined symbol.
Finally, this patch updates README.md to both make some revisions to
account for the UART support introduced in previous patches as well as
to provide instructions for using the UEFI support.
This patch modifies the newlib and Contiki C and C++ compiler flags to
omit exception handling unwind tables (see
http://wiki.dwarfstd.org/index.php?title=Exception_Handling).
Removing these tables saves space in debug builds and has not caused
any readily-apparent functional changes.
Here is the size listing for an example program built without this
patch:
text data bss dec hex filename
76002 1508 21224 98734 181ae all-timers.galileo
Here is the size listing for the same program with this patch:
text data bss dec hex filename
72918 1508 21224 95650 175a2 all-timers.galileo
The primary motivation for this patch is to help enable UEFI support.
The .eh_frame and .eh_frame_hdr sections that are otherwise generated
are treated as code sections by the EDK2 GenFw program, since they are
read-only alloc sections. They get grouped with the actual code
sections, ahead of the data sections. This perturbs symbols and
complicates debugging.
This patch adds support for Ethernet to the Intel Galileo port. It
uses the Intel Quark X1000 Ethernet driver. It initializes the first
Ethernet interface and starts some common network services. By
default, it uses the following addresses:
- Host: 192.0.2.2
- Netmask: 255.255.255.0
- Default gateway: 192.0.2.1
- DNS server: (same as default gateway)
These settings can be changed by editing eth-conf.c.
This patch adds the galileo-pinmux.c and galileo-pinmux.h files,
which support access to pinmux configuration through a function
interface.
This is not 100% supported yet due to some pinmux paths
need Quark X1000 GPIO (legacy and non-legacy) configurations.
After we finish to implement Quark X1000 GPIO driver we'll add
support for this.
This patch adds pwm-pca9685.c and pwm-pca9685.h files,
which support access to I2C-based PCA9685 PWM controller
configuration register through a function interface.
The PCA9685 is an I2C-bus controlled 16-channel LED controller
optimized for Red/Green/Blue/Amber (RGBA) color backlighting
applications. Each LED output has its own 12-bit resolution
(4096 steps) fixed frequency individual PWM controller that
operates at a programmable frequency from a typical of 24 Hz to
1526 Hz with a duty cycle that is adjustable from 0 % to 100 %
to allow the LED to be set to a specific brightness value.
More about PCA9685 can be found in its datasheet[1].
This driver is needed in order to configure Galileo pinmux.
[1] - http://www.nxp.com/documents/data_sheet/PCA9685.pdf
This patch adds gpio-pcal9535a.c and gpio-pcal9535a.h files,
which support access to I2C-based PCAL9535A GPIO controller
configuration register through a function interface.
The PCAL9535A is a low-voltage 16-bit GPIO expander with interrupt
and reset for I2C-bus/SMBus applications. It contains the PCA9535
register set of four pairs of 8-bit Configuration, Input, Output,
and Polarity Inversion registers, and additionally, the PCAL9535A has
Agile I/O, which are additional features specifically designed to
enhance the I/O. More about PCAL9535A can be found in its datasheet[1].
This driver is needed in order to configure Galileo pinmux.
[1] - http://www.nxp.com/documents/data_sheet/PCAL9535A.pdf
This patch adds -ffunction-sections and -fdata-sections to the
'release' CFLAGS so each function and data is place into its
own section in the output file. It also adds --gc-section to
the 'release' LDFLAGS so the linker removes the sections which
are not referenced.
This patch also adds -ffunction-sections and -fdata-sections
options to CFLAGS from build_newlib.sh. This increases newlib
static libraries size, however, the Contiki image shrinks even
more since --gc-section removes "dead code" from newlib.
As a practical effect, all unused function and data (as well as
sections such as .eh_frame) are striped out from the final elf
binary. This shrinks our release binary drastically.
Finally, to prevent --gc-section from removing .multiboot section,
this patch adds KEEP(*(.multiboot)) to quarkX1000.ld.
This patch slightly revises CFLAGS and LDFLAGS to specify the
optimization and debugging options and linker script in a way that is
compatible with using Clang as the C compiler and to invoke the linker
(i.e. CC = clang and LD = clang).
This patch modifies the include order to include headers from newlib
ahead of those from the core of Contiki. The only header file names
that are common between Contiki and newlib are assert.h and config.h,
but the config.h files in Contiki are only located in ports for other
CPUs so they are irrelevant to this patch. The motivation for this
patch is to cause files that include assert.h to include the one from
newlib that halts when an assertion fails. The assert implementation
in the core of Contiki does not halt when an assertion fails.
This patch also adds newlib syscall stubs that are required by the
newlib assert implementation and the _exit syscall function that halts
the system.
Finally, this patch updates some other newlib syscall stubs to
properly indicate their status as unsupported syscalls.
This patch revises README.md to mention the UART support introduced by
earlier patches in the section about verifying that Contiki is
running. It also revises the serial console setup instructions to
focus on the more thoroughly tested option.
This patch removes 'newlib-syscalls.c' from CONTIKI_SOURCEFILES variable
and appends it to PROJECT_SOURCEFILES. This way the buildsystem will
automatically consider the newlib-syscalls object code during linking
time.
This patch adds support for building release images. The main difference
between release images and default images is that the former is optimized
for size while the latter is "optimized" for debugging. To build a release
image, the BUILD_RELEASE variable should be set to 1. For instance, the
following command build a release image from the hello-world application:
$ cd examples/hello-world && make TARGET=galileo BUILD_RELEASE=1
To optimize for size we use the '-Os' option from gcc. This option also
enables the strict aliasing optimization. This generates lots of warning
messages since we use the '-Wall' option and lots of code in core/net/
break the strict-aliasing rules. Some test have shown that the strict
aliasing optimization it not taking effect in the final binary. For that
reasons, this patch manually disables the optimization. Also, the release
image is stripped.
For the sake of comparison, below follows the output from 'wc' and 'size'
for both debugging (default) and release images.
Default image:
$ wc -c hello-world.galileo
71112 hello-world.galileo
$ size hello-world.galileo
text data bss dec hex filename
20379 1188 12808 34375 8647 hello-world.galileo
Release image:
$ wc -c hello-world.galileo
26320 hello-world.galileo
$ size hello-world.galileo
text data bss dec hex filename
18146 1156 12808 32110 7d6e hello-world.galileo
This patch removes _kill_r and _getpid_r stubs since they are not
required by newlib at this moment. These stubs should not be in
the commit that introduced the initial newlib-syscalls.c file.
This patch introduces the initial support for stdio library in Galileo
platform. For now, only standard output and error are supported. Both
streams use the UART1 device.
Newlib doesn't call open() for stdin, stdout, and stderr which means
that the _write_r call is the first activity the stub will see on
those streams. For that reason, we initialize the UART1 device in
Galileo's platform main() function instead of in open() system call.
This patch implements the _sbrk_r() system call for Galileo platform. This
system call is required by newlib's malloc() implementation. Next patch
will introduce the initial support for stdio library which requires a
working malloc() function for proper operation.
We are not sure about the heap size we should use. Preliminary tests
have shown that stdio library requests 1032 bytes heap. So, as an initial
guess, a 2Kb heap size should be enough for now.
This patch enhances build_newlib.sh to create Makefile.libc so that
the main Galileo makefile can attempt to include Makefile.libc and
instruct the developer to run build_newlib.sh first if the definition
within Makefile.libc is not detected.
This patch moves the compiler and linking options related to QuarkX1000
SoC to Makefile.x86_quarkX1000 since it is more suitable. For instance,
'-m32' should be used in any platform based on QuarkX1000, not only
Galileo. The same rationale applies for the others options (e.g. -march,
mtune).
The CFLAGS setting used for the newlib build process includes
"-mtune=i586" as does the ASFLAGS setting used for the Contiki build
process. However, the CFLAGS setting used for the Contiki build
process did not include that flag. This patch adds it for
consistency.
Ubuntu enables GCC's stack protector by default (see
https://wiki.ubuntu.com/Security/Features). This causes link errors
like the following:
...undefined reference to `__stack_chk_fail'
To avoid these errors, this patch adds the "-fno-stack-protector" flag
to both the CFLAGS used by the Contiki build process and the CFLAGS
used by the newlib build process.
This is a refactoring patch, no functionality is changed. It moves
loader.S and galileo.ld from platform/galileo/ to cpu/x86/ directory
since they seem to be more SoC-specific than platform-specific.
It also renames galileo.ld to quarkX1000.ld since it can be used by
any platform based on Quark X1000 SoC, not only Galileo.
Furthermore, this patch also renames loader.S to bootstrap_quarkX1000.S
since it is pretty much a bootstrap code to any platform based on Quark
X1000 SoC.
Now the cpu/x86/ provides a Makefile.x86_common and a
Makefile.x86_pc. The former includes the common Makefile
and adds legacy pc specific implementations (currently,
drivers only) into the building context, while the latter
has everything that defines the bootstrap of a x86 CPU.
This commit also fixes platform/galileo/ so it includes the
correct makefile - Makefile.x86_quarkX1000. Galileo uses
a Quark X1000 SoC which is not an IBM Generic PC-like CPU,
but it does provide most of a PCs peripherals through
its "Legacy Bridge". Thus, it makes sense that QuarkX1000's
Makefile includes code from the legacy_pc x86 cpu.
All drivers implemented so far are for chips which are only available
on legacy x86 PCs. This commit moves them into a more appropriate folder,
also making the cpu/x86/drivers/ folder ready for other x86 based SoCs.
Currently, it is common to see Contiki's core/ interfaces implementations
spread in both cpu/ and platform/. We here take one step further starting
an effort to centralize all of these in platform's code instead.
This commit starts this by adding platform/galileo/core/ and its sys/
subfolder, adding a stubbed mtarch.h and moving clock and rtimer
implementations to this new folder. From now on we should concentrate
implementation from Contiki's core/ interfaces into the appropriate
subfolder in platform/galileo/core/.
Note that this is not the current fashion followed on other platforms
and cpus folders, as most of them add the core interface implementation
into its subfolder directly. For instance, on CC2538DK,
core/dev/button-sensor.h is implemented in platform/cc2538dk/dev/
directly, while on Galileo it would sit at platform/galileo/core/dev/.
We believe ours is a better approach to organize and escalate a
platform's code base.
We also remove previous x86 mtarch.h and mtarch.c since they weren't used
at all - both native and cooja platforms have their own mtarch
implementations.
This patch adds support for rtimer library on Galileo's platform.
We use the PIT to implement the rtimer platform dependent
functionalities. We chose the PIT for mainly two reason: I) its
configuration is very simple II) it has a high frequency which
provides us a good clock resolution (requirement from rtimer
library).
Since we keep track of the number of ticks in software, we define
rtimer_clock_t type as uint64_t. This gives us a good amount of time
til the variable overflows. For instance, a 32-bit type would overflow
in about one hour for high clock resolution (~ 1us).
The rtimer clock frequency (RTIMER_ARCH_SECOND) is setup to 1 kHz.
There is no technical matter regarding this value. It is just an
initial guess.
Just for the record, we might want to use HPET in future to
implement the rtimer library since it seems to be more appropriate.
The reason why we don't use it at this moment is that, in order to
configure it, we need support for ACPI 2.0 which we don't. Once we
have use-cases for the rtimer library we'll probably replace PIT
by HPET or any other timer more suitable for the job.
This patch adds support for the Etimer and Ctimer libraries. To support
the Etimer library, we should poll the etimer process every time the
system clock is updated. To do this more efficiently, by taking advantage
of etimer_next_expiration_time() API, we poll the etimer process only
when an 'Event Timer' has expired.
We don't need any platform specific support in order to enable the Ctimer
library since it relies completely on Etimer.
The others timer libraries (Timer and Stime) don't required any specific
platform support as well since they rely on the system Clock module only.
This patch adds support for Contiki's clock module. All functions from
core/sys/clock.h are implemented, except clock_set_seconds() and clock_
delay_usec(). The CLOCK_CONF_SECOND macro is set to 128. This value
seems to be good enough since several platforms used it. Finally, we
use the RTC driver to track the number of ticks from the system clock.
The Programmable Interrupt Controller is a chip responsible for
translating hardware interrupts to system interrupts. When it
receives an Interrupt Request (IRQ), it triggers the appropriate
interrupt line reaching the appropriate IDT gate, following a
previously setup offset.
There are 2 daisy-chained PICs. PIC1 handles IRQs 0-7 and PIC2
handles IRQs 8-15. If no vector offset is set, an IRQ0, for instance,
would trigger the interrupt 0, clashing with the "Division by zero exception"
handler. Thus the IRQs must be remapped.
This patch implements the PICs initialization through their 4
Initialization Command Words (ICWs) in a very "canonical" way:
- ICW1: the initializing command;
- ICW2: the vector offset for the PIC1 and PIC2 (we add an offset of 32 positions);
- ICW3: the inter-PICs wiring setup (we connect PIC2 to PIC1's IRQ2);
- ICW4: extra systems information (we set PIC1 as Master and PIC2 as slave).
It then masks the Interrupt Mask Register, blocking all IRQs but #2 initially.
These must be unmasked on demand. The IMR is 8-bits long, so setting the n^th bit to 1
would DISABLE the IRQ n while setting it to 0 would ENABLE IRQ n.
As stated, this is an implementation of the legacy 8259 PIC. More
investigation is needed so we decide if it is enough or if we need
the (newer) APIC implementation instead.
This patch also adds the outb() helper function to helpers.h. The helpers
is a wrapper for assembly 'out' instruction.
Finally, since we now properly support hardware interrupts, this patch
also enables IRQs in platform main().
More information:
- Quark X1000 Datasheet, section 21.12, page 898.
- http://wiki.osdev.org/8259_PIC
- http://stanislavs.org/helppc/8259.html
This patch defines the cpu_init() function which should encapsulate
all code related to x86 CPU initialization. For now, this function
initializes GDT and IDT.
This patch adds the helpers.h. This file should contain only x86-related
helper functions and macros. For now, we define the BIT macro and halt()
helpers which will be used in upcoming patches.
Additionally, this patch also changes loader.S to call the halt().
This patch implements the main() function for Galileo platform. At this
moment, only Processes subsystem is enabled. After this patch we are
able to some rudimentary debugging to ensure that process thread from
applications are being indeed executed.
Once we properly support more Contiki subsystems, such as clock, ctimer,
etimer, and rtimer, we will add them to Galileo platform's main() as well.
All we need to provide to C at this point is a region in memory dedicated to
its stack. This is done by allocating a region in .bss and pushing its start
address to esp. Since the multiboot spec says it is not safe to rely on the
initial stack provided by the bootloader, this patch provides our own stack.
Galileo boards have 512Kb of SRAM and 256Mb of DDR3 RAM, so providing 8kb as
a start seems safe. Moreover, stack sizes are very application-oriented
so it may be too early to provide a bigger (or smaller) stack.
This patch changes Galileo's buildsystem to print the elf sections
sizes after a new image is built. This way we can easily track how
these sections increase or decrease after any change.
To achieve that, we define a custom linking rule which is pretty much
the same as the default linking rule define in Makefile.include, but
we run 'size' command after the image is built.
This patch adds a README file which contains general information about
the Intel Galileo board support. The file provides information about
supported features as well as instructions on how to build, run and debug
applications for this platform.
This patch the 'debug' rule to simplify the debugging process. This new
rule runs OpenOCD and gdb with the right parameters. OpenOCD runs in
background and its output will be redirected to a log file in the
application's path called LOG_OPENOCD. Once gdb client is detached,
OpenOCD is terminated.
The 'debug' rule is defined in Makefile.customrules-galileo file (create
by this patch) which is included by the Contiki's buildsystem. So to
debug a Contiki application for Galileo board, run the following command:
$ make TARGET=galileo debug
If you use a gdb front-end, you can define the "GDB" environment variable
and your gdb front-end will be used instead of default gdb. For instance,
if you want to use cgdb front-end, just run the command:
$ make BOARD=galileo debug GDB=cgdb
This patch adds the initial support for Intel Galileo Platform. It
contains the minimum set of code required to boot a dummy Contiki
image.
For Galileo initial support, we implemented a linker script, a minimal
bootstrap code, a set of stubbed functions required by newlib, and a
very simple main() function. Moreover, we also define some header files
and macros required by Contiki.
To build applications for this platform you should first build newlib
(in case it wasn't already built). To build newlib you can run the
following command:
$ platform/galileo/bsp/libc/build_newlib.sh
Once newlib is built, you can build applications. To build applications
for Galileo platform you should set TARGET variable to 'galileo'. For
instance, building the hello-world application should look like this:
$ cd examples/hello-world/ && make TARGET=galileo
This will generate the 'hello-world.galileo' file which is a multiboot-
compliant [1] ELF image. This image can be booted by any multiboot-
complaint bootloader such as Grub.
Finally, this patch should be used as a guideline to add the initial
support for others platforms based on x86 SoCs.
[1] https://www.gnu.org/software/grub/manual/multiboot/multiboot.html
This patch creates the platform/galileo/bsp directory. This directory
contain all files related to Galileo's Board Support Package (BSP). For
now, the BSP consists of libc and bootloader.
Within the BSP directory, we have the scripts build_newlib.sh and build_
grub.sh. These scripts provide an easy and quick way to build the newlib
and the grub for the Galileo platform.
Currently there are only one platform using CPU x86: Cooja. The
elfloader-x86.c is rather a POSIX implementation, so the Galileo port
won't use it for now. This patch fixes this by moving this source file to
be included by the platforms using it instead of the cpu's Makefile.
Coffee is placed by default at the beginning of the flash memory, right
before the firmware. This avoids the memory gaps that there could be
before and after Coffee if it were placed after the firmware, because it
is unlikely that the end of the firmware is aligned with a flash page
boundary, and the CCA is not flash-page-aligned. Thanks to that, Coffee
is also always in the same flash area if its size remains unchanged,
even if the firmware changes, which makes it possible to keep the Coffee
files when reprogramming the firmware after a partial flash erase
command.
The default configuration of Coffee is set to use sensible values for a
typical usage on this SoC, i.e. for sensor data logging.
The default size of Coffee is set to 0 in order not to waste flash if
Coffee is unused.
COFFEE_CONF_CUSTOM_PORT can be defined to a header file to be used with
"#include" in order to override the default CC2538 port of Coffee. This
makes it possible to use Coffee with an external memory device rather
than with the internal flash memory, without having to alter the Contiki
files.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
Depending on the linker script, the generated .bin file may start beyond
the beginning of the flash memory. However, no target address was passed
to cc2538-bsl.py by the upload make target, so it used the beginning of
the flash memory in all cases.
The load address of the lowest loadable output section is now passed to
cc2538-bsl.py. The start address of the .text output section or the
address of the _text symbol could have been used too, but this would not
have been compatible with all the possible custom linker scripts.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
Define the available CC2538 devices and their features, and use them to
define the linker script memory regions. The .nrdata output section is
now always defined in order to trigger an error if it is used but no
memory is available for it. The CC2538 device used by Contiki is made a
configuration option, the CC2538SF53 device being the default.
This makes more sense than defining the flash memory address and size as
configuration options like previously, all the more not all values are
possible and all the features are linked by each device.
This change also makes it possible to:
- use the correct SRAM parameters for the CC2538NF11,
- know at build time if the AES, SHA, ECC and RSA hardware features are
available on the selected CC2538 device.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
This commit fixes nearly all of the reported doxygen warnings.
I tried to not clutter the log with removed trailing spaces.
Removed whitespace and converted tab/spaces for all files affected by this commit
are in a separate branch.
CC_FASTCALL was introduced many years ago for the cc65 tool chain. It was never used for another tool chain. With a798b1d648 the cc65 tool chain doesn't need CC_FASTCALL anymore.
Recently support for 80 column CONIO based on 320x200 graphics was added to the cc65 C library for the C64. This change leverages this for the IRC client and the web browser. Because not everybody prefers this 'soft80' display with its small 4x8 charbox the 40 column programs are still available as before (with the new programs called 'irc80' and 'webbrowser80').
So far 80 column display was an attribute of a cc65 platform. Now each cc65 application can ask for 80 column display by defining WITH_80COL. Of course this is ignored by platforms incapable of 80 column display.
I see three types of application:
* Applications not benefitting from 80 column at all and in fact looking better with 40 column display. These are now using 40 column display. Examples: ethconfig, ipconfig
* Applications taking advantage of 80 column display if it is available without drawbacks. These stay as they were. Examples: Telnet server, web server, wget
* Applications needing 80 column display so urgently that it is likely desirable even if the display becomes harder to read. These come now in both flavors allowing the user to choose. Examples: IRC, web browser
Note: This change doesn't actually introduce any 80 column display with drawbacks. This if left to a subsequent change.
The cc65 memory map for the ATARI XL has two holes so the linker needs hints which object files go where. Source changes lead to object file size changes requiring now and then to rearrange the object files.
