Comprehensive Real-World Guidance for Every Embedded Developer and Engineer
This book brings together indispensable knowledge for building efficient, high-value, Linux-based embedded products: information that has never been assembled in one place before. Drawing on years of experience as an embedded Linux consultant and field application engineer, Christopher Hallinan offers solutions for the specific technical issues you're most likely to face, demonstrates how to build an effective embedded Linux environment, and shows how to use it as productively as possible.
Hallinan begins by touring a typical Linux-based embedded system, introducing key concepts and components, and calling attention to differences between Linux and traditional embedded environments. Writing from the embedded developer's viewpoint, he thoroughly addresses issues ranging from kernel building and initialization to bootloaders, device drivers to file systems.
Hallinan thoroughly covers the increasingly popular BusyBox utilities; presents a step-by-step walkthrough of porting Linux to custom boards; and introduces real-time configuration via CONFIG_RT--one of today's most exciting developments in embedded Linux. You'll find especially detailed coverage of using development tools to analyze and debug embedded systems--including the art of kernel debugging.
• Compare leading embedded Linux processors
• Understand the details of the Linux kernel initialization process
• Learn about the special role of bootloaders in embedded Linux systems, with specific emphasis on U-Boot
• Use embedded Linux file systems, including JFFS2--with detailed guidelines for building Flash-resident file system images
• Understand the Memory Technology Devices subsystem for flash (and other) memory devices
• Master gdb, KGDB, and hardware JTAG debugging
• Learn many tips and techniques for debugging within the Linux kernel
• Maximize your productivity in cross-development environments
• Prepare your entire development environment, including TFTP, DHCP, and NFS target servers
• Configure, build, and initialize BusyBox to support your unique requirements
8.2.7. modinfo
8.2.7. modinfo
You might have noticed the last three lines of the skeletal driver in Listing 8-1, and later in Listing 8-6. These macros are there to place tags in the binary module to facilitate their administration and management. Listing 8-9 is the result of modinfo executed on our hello1.ko module.
Listing 8-9. modinfo Output
$ modinfo hello1
filename: /lib/modules/.../char/examples/hello1.ko
author: Chris Hallinan
description: Hello World Example
license: GPL
vermagic: 2.6.14 ARMv5 gcc-3.3
depends:
parm: debug_enable:Enable module debug mode. (int)
$
The first field is obvious: It is the full filename of the device driver module. For readability in this listing, we have truncated the path again. The next lines are a direct result of the descriptive macros found at the end of Listing 8-6 namely, the filename, author, and license information. These are simply tags for use by the module utilities and do not affect the behavior of the device driver itself. You can learn more about modinfo from its man page and the modinfo source itself.
One very useful feature of modinfo is to learn what parameters the module supports. From Listing 8-9, you can see that this module supports just one parameter. This was the one we added in Listing 8-6, debug_enable. The listing gives the name, type (in this case, an int), and descriptive text field we entered with the MODULE_PARM_DESC() macro. This can be very handy, especially for modules in which you might not have easy access to the source code.
