Custom Linux Kernel Development - Revision history

Mdean: Updated to use new templates.

2015-11-12T00:14:34Z

Updated to use new templates.

Mgloff at 21:29, 10 November 2015

2015-11-10T21:29:17Z

Bserrano at 19:59, 14 April 2014

2014-04-14T19:59:02Z

Bserrano at 21:28, 27 March 2014

2014-03-27T21:28:33Z

Mdean: Improved kernel newbies link description; tagged MW to review for Complete status.

2014-03-20T16:36:37Z

Improved kernel newbies link description; tagged MW to review for Complete status.

Tstratman: grammar correctification

2014-03-20T04:51:53Z

grammar correctification

Tstratman: /* Testing */ fixed italics

2014-03-20T04:49:20Z

‎Testing: fixed italics

Tstratman: /* Where to go for Additional Information */ added link, fixed spacing

2014-03-20T04:47:37Z

‎Where to go for Additional Information: added link, fixed spacing

Tstratman: minor edits

2014-03-20T04:43:01Z

minor edits

Mdean: Made more changes; marked for final draft, but asking Travis to approve changes before getting another reviewer.

2014-03-18T18:40:23Z

Made more changes; marked for final draft, but asking Travis to approve changes before getting another reviewer.

@@ Line 1: / Line 1: @@
-{{todo|Complete (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+);(04.14.14-15:00->BS+);(11.10.15-15:30->MG+)|Travis Stratman|project=oe 5,TS,bs,SEOKWREV,Complete,mg,mw}}
+{{todo|Complete (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+);(04.14.14-15:00->BS+);(11.10.15-15:30->MG+)(11.11.2015-18:15->MD+)|Travis Stratman|project=oe 5,TS,bs,Complete,mg,mw,md}}
 {{#seo:
@@ Line 25: / Line 25: @@
 Source code for EMAC kernels is provided through our Git server. Refer to the documentation for your system to determine the correct source to use.
-{{mbox|type=notice|text=For this guide, the 2.6.30-at91 kernel tree will be used. This kernel tree currently covers many of EMAC OE 4's SoM-based ARM products.}}
+{{ note | For this guide, the 2.6.30-at91 kernel tree will be used. This kernel tree currently covers many of EMAC OE 4's SoM-based ARM products.}}
 === Clone the Git Repository ===
 To clone the git repository over anonymous HTTP, run the following commands:
-<syntaxhighlight lang=bash>
-developer@ldc:~$ git clone http://git.emacinc.com/public/source/linux-2.6.30-at91.git
+{{ cli | username=developer | hostname=ldc |<nowiki>git clone http://git.emacinc.com/public/source/linux-2.6.30-at91.git</nowiki>}}
 Once the command has completed, the entire source should be contained in the <code>linux-2.6.30-at91</code> directory. The ''master'' branch will be checked out automatically. Because EMAC uses the ''master'' branch for all releases, this is the correct branch to use, but other branches or tags may be checked out if directed or required.
@@ Line 96: / Line 95: @@
 Once created, the current kernel configuration is stored in a file named <code>.config</code> in the top level of the kernel source tree. This file is read and updated by the configuration utility and is used by the <code>make</code> system during the build process. The first step in configuring the kernel often involves initializing this file with a default configuration providing sane values for the target platform. These default configuration files are stored under the <code>arch</code> directory. For example, <code>arch/arm/configs/</code> holds default configuration files for ARM targets.
-{{mbox|type=notice|text=Note that the <code>.config</code> file is a hidden file since its filename begins with a <code>'.'</code>. The <code>ls</code> utility will not show this file by default unless the <code>-a</code> option is passed to show hidden files.}}
+{{ note | Note that the <code>.config</code> file is a hidden file since its filename begins with a <code>'.'</code>. The <code>ls</code> utility will not show this file by default unless the <code>-a</code> option is passed to show hidden files.}}
 In this example, copy the <code>arch/arm/configs/som9g45-som210_defconfig</code> file to the top level of the kernel source as <code>.config</code>:
-<syntaxhighlight lang=bash>
-developer@ldc:~$ cp arch/arm/configs/som9g45-som210_defconfig .config
+{{ cli | username=developer | hostname=ldc |cp arch/arm/configs/som9g45-som210_defconfig .config}}
-</syntaxhighlight>
 This is the default configuration file for the EMAC SoM-9G45 module using an SoM-210ES carrier board.
@@ Line 131: / Line 130: @@
 </syntaxhighlight>
-{{mbox|type=notice|text=While editing the configuration file by hand is not recommended because it is easy to break dependencies that the configuration utility will catch, viewing the configuration file as text can be helpful in quickly exposing the current configuration selections.  The <code>grep</code> utility is often helpful when checking a kernel configuration file to determine the setting of a specific option.}}
+{{ note | While editing the configuration file by hand is not recommended because it is easy to break dependencies that the configuration utility will catch, viewing the configuration file as text can be helpful in quickly exposing the current configuration selections.  The <code>grep</code> utility is often helpful when checking a kernel configuration file to determine the setting of a specific option.}}
 === Configuring the Kernel ===
@@ Line 157: / Line 156: @@
 One common kernel development task when working with EMAC systems is adding support for a new custom carrier board for use with an EMAC SoM. In general, the procedure for this task is to use one of the existing EMAC carrier board support files as a base and make adjustments as needed to support the custom hardware. Additions to the <code>Makefile</code>s and <code>Kconfig</code> are also generally required to add new selections to the kernel configuration and build system. This section covers an example of the work required for this using the SoM-9G45 module as an example.
-{{mbox|type=notice|text=Note that the process described below is somewhat tailored to the 2.6.30-at91 kernel tree and will not be applicable directly to systems which use different kernels without some modification. The intent is to familiarize the reader with the task of adding support for a custom carrier board using this as a specific example. Contact EMAC if you require more information on how to do this for your target system.}}
+{{ note | Note that the process described below is somewhat tailored to the 2.6.30-at91 kernel tree and will not be applicable directly to systems which use different kernels without some modification. The intent is to familiarize the reader with the task of adding support for a custom carrier board using this as a specific example. Contact EMAC if you require more information on how to do this for your target system.}}
 === Machine-Specific Support Files ===
@@ Line 164: / Line 163: @@
 The board support file for the SoM9G45 is <code>board-som9m10g45.c</code>. You will see that it contains code for devices inherent to the module, such as the flash, LCD, Ethernet PHY, and micro-SD (MMC), as well as references to the <code>cspec</code> ("carrier specification") structure. The carrier specification structure is defined by code in the carrier board file. It determines which devices are enabled and how they are configured to match the features of the target carrier board.
-{{mbox|type=notice|text=Note that this method of board support configuration changed dramatically in more recent kernel series with the ''Device Tree'' structure.}}
+{{ note | Note that this method of board support configuration changed dramatically in more recent kernel series with the ''Device Tree'' structure.}}
 For example, in the <code>som_board_init()</code> function, SPI support is configured with the following lines:
@@ Line 230: / Line 229: @@
 === Example New Carrier Board Support Files ===
 Suppose that support for a new carrier board is required and utilizes hardware very similar to the SoM-210ES. For the purposes of this example, assume that the name of the product is ''FTS''. To implement support for this hardware, start by copying the <code>emac-carrier/board-som210.c</code> file to <code>emac-carrier/board-fts.c</code> and follow the steps below to add support to the kernel for this new board.
-<syntaxhighlight lang=console>
-developer@ldc:~/linux/arch/arm/mach-at91/emac-carrier$ cp board-som210.c board-fts.c
+{{ cli | username=developer | hostname=ldc | pwd=~/linux/arch/arm/mach-at91/emac-carrier |cp board-som210.c board-fts.c}}
 ==== Kconfig and Makefile Additions ====
@@ Line 313: / Line 311: @@
 </syntaxhighlight>
-{{mbox|type=notice|text=Note that the <code>spi0cs1</code> device is an EMAC SPI Class device. See [[EMAC SPI Programming]] for  more information on how to utilize this interface.}}
+{{ note | Note that the <code>spi0cs1</code> device is an EMAC SPI Class device. See [[EMAC SPI Programming]] for  more information on how to utilize this interface.}}
 ===== Programmable Clocks =====

← Older revision		Revision as of 21:29, 10 November 2015
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−	{{todo\|~~FinalDraft~~ (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+);(04.14.14-15:00->BS+)\|Travis Stratman\|project=oe 5,TS,bs,SEOKWREV,~~FinalDraft~~,mw}}	+	{{todo\|Complete (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+);(04.14.14-15:00->BS+);(11.10.15-15:30->MG+)\|Travis Stratman\|project=oe 5,TS,bs,SEOKWREV,Complete,mg,mw}}

	{{#seo:		{{#seo:

@@ Line 1: / Line 1: @@
-{{todo|FinalDraft (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+)|Travis Stratman|project=oe 5,TS,bs,SEOKWREV,FinalDraft,mw}}
+{{todo|FinalDraft (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+);(04.14.14-15:00->BS+)|Travis Stratman|project=oe 5,TS,bs,SEOKWREV,FinalDraft,mw}}
 {{#seo:
 |title=Custom Linux Kernel Development
 |titlemode=append
-|keywords=Linux Kernel Development,Kernel Source,Git Repository,Kernel Source Structure,Configuring Kernel,Driver Development
+|keywords=Linux Kernel Development,Git Repository,Kernel Source Structure
 |description=Provide information on the most common kernel development tasks for EMAC OE Linux systems.
 }}

← Older revision		Revision as of 21:28, 27 March 2014
Line 1:		Line 1:
−	{{todo\|~~Final Draft~~ (03.18.14-13:40->MD+)(03.20.14-11:35->MD+)\|Travis Stratman\|project=oe 5,TS,bs,~~SEOKWTODO~~,FinalDraft,mw}}	+	{{todo\|FinalDraft (03.18.14-13:40->MD+)(03.20.14-11:35->MD+);(03.27.14-16:25->BS+)\|Travis Stratman\|project=oe 5,TS,bs,SEOKWREV,FinalDraft,mw}}

		+	{{#seo:
		+	\|title=Custom Linux Kernel Development
		+	\|titlemode=append
		+	\|keywords=Linux Kernel Development,Kernel Source,Git Repository,Kernel Source Structure,Configuring Kernel,Driver Development
		+	\|description=Provide information on the most common kernel development tasks for EMAC OE Linux systems.
		+	}}
	The ability to easily customize and expand any portion of the kernel is a feature of Linux that makes it very well suited for embedded systems development. In the embedded environment, specialized hardware, protocols, and systems may require a look into the kernel internals, custom configuration, feature additions, or driver development. This article aims to provide information on the most common kernel development tasks for EMAC OE Linux systems as well as additional kernel development resources.		The ability to easily customize and expand any portion of the kernel is a feature of Linux that makes it very well suited for embedded systems development. In the embedded environment, specialized hardware, protocols, and systems may require a look into the kernel internals, custom configuration, feature additions, or driver development. This article aims to provide information on the most common kernel development tasks for EMAC OE Linux systems as well as additional kernel development resources.

@@ Line 1: / Line 1: @@
-{{todo|Final Draft (03.18.14-13:40->MD+)|Travis Stratman|project=oe 5,TS,bs,SEOKWTODO,FinalDraft}}
+{{todo|Final Draft (03.18.14-13:40->MD+)(03.20.14-11:35->MD+)|Travis Stratman|project=oe 5,TS,bs,SEOKWTODO,FinalDraft,mw}}
 The ability to easily customize and expand any portion of the kernel is a feature of Linux that makes it very well suited for embedded systems development. In the embedded environment, specialized hardware, protocols, and systems may require a look into the kernel internals, custom configuration, feature additions, or driver development. This article aims to provide information on the most common kernel development tasks for EMAC OE Linux systems as well as additional kernel development resources.
@@ Line 467: / Line 467: @@
 : This book is available online in free PDF form through the [http://lwn.net/Kernel/LDD3 LWN.net site]. It is also available in-print through O'Reilly. LDD3 covers most of the topics required for Linux kernel development and includes examples. Note that some of the APIs covered have changed since 2.6.10 when the book was written so adaptation may be required to use the example code.
 ; Kernel Newbies
-: The [http://kernelnewbies.org/ Kernel Newbies] website provides information for people new to working with the Linux kernel and device drivers. The site is still a work in progress, but has some valuable information for working with the Linux kernel. It also maintains a [http://kernelnewbies.org/LinuxChanges Kernel Changelog], which is a page that gives a plain English description of the features and bugfixes which went into the kernel. The changelog also includes links to pages on other sites which provide more details on specific features and/or fixes which went into the kernel version being described. By default, the page lists the changes to the latest stable release of the kernel. The changlogs for older releases can can be viewed by appending an underscore followed by the version number (major and minor numbers only) of the kernel for which you wish to see changes to the base URL for the page (http://kernelnewbies.org/Linux). For example, to examine the changelog for the 3.12 kernel, take the base URL, http://kernelnewbies.org/Linux, and append _3.12 to form [http://kernelnewbies.org/Linux_3.12 http://kernelnewbies.org/Linux_3.12].
+: The [http://kernelnewbies.org/ Kernel Newbies] website provides information for people new to working with the Linux kernel and device drivers. The site is still a work in progress, but has some valuable information for working with the Linux kernel. It also maintains a [http://kernelnewbies.org/LinuxChanges Kernel Changelog], which is a page that gives a plain English description of the features and bugfixes which went into the latest kernel release. The changelog also includes links to pages on other sites which provide more details on specific features and/or fixes which went into the kernel version being described. The changelogs which were made for previous kernel versions can be found [http://kernelnewbies.org/LinuxVersions here].
 ; Mailing Lists
 : There are many very active mailing lists (see http://vger.kernel.org/vger-lists.html) that can be used to ask questions or search through archives for solutions. The archive of the Linux Kernel mailing list is available at [https://lkml.org/ LKML.org] and archives to other lists can be found through a web search as well as links noted in the list [http://vger.kernel.org/vger-lists.html here].

@@ Line 169: / Line 169: @@
 </syntaxhighlight>
-The first call to <code>at91_add_device_spi()</code> adds devices present on the SoM itself, while the next lines check to see if the carrier board specification indicates that SPI is utilized and adds all devices in the carrier board spi configuration. The carrier support functions and definitions are included through <code>arch/arm/mach-at91/include/mach/emac-carrier.h</code>.
+The first call to <code>at91_add_device_spi()</code> adds devices present on the SoM itself, while the next lines check to see if the carrier board specification indicates that SPI is utilized and add all devices in the carrier board spi configuration. The carrier support functions and definitions are included through <code>arch/arm/mach-at91/include/mach/emac-carrier.h</code>.
 === Carrier Board-Specific Support ===

@@ Line 410: / Line 410: @@
 === Testing ===
-After making the development changes required to support a new carrier board, you must change the kernel configuration to specify the new carrier board. Using the menu configuration utility described in the [[#Menuconfig|Menuconfig section]], navigate to 'System Type -> Atmel AT91 System-on-Chip -> EMAC Carrier Board Selection''. The list should now have a choice for ''FTS Carrier Support''. Highlight this option and press enter. Finally, exit and save the configuration.
+After making the development changes required to support a new carrier board, you must change the kernel configuration to specify the new carrier board. Using the menu configuration utility described in the [[#Menuconfig|Menuconfig section]], navigate to ''System Type -> Atmel AT91 System-on-Chip -> EMAC Carrier Board Selection''. The list should now have a choice for ''FTS Carrier Support''. Highlight this option and press enter. Finally, exit and save the configuration.
 Following the steps described in [[#Building and Deployment|Building and Deployment]] above, compile the kernel and load it to your target hardware. Test all functionality, particularly new devices that were added to the carrier board support file, and make adjustments as necessary.

@@ Line 1: / Line 1: @@
-{{todo|Review|Travis Stratman|project=oe 5,TS,bs,SEOKWTODO,Review}}
+{{todo|Final Draft (03.18.14-13:40->MD+)|Travis Stratman|project=oe 5,TS,bs,SEOKWTODO,FinalDraft}}
 The ability to easily customize and expand any portion of the kernel is a feature of Linux that makes it very well suited for embedded systems development. In the embedded environment, specialized hardware, protocols, and systems may require a look into the kernel internals, custom configuration, feature additions, or driver development. This article aims to provide information on the most common kernel development tasks for EMAC OE Linux systems as well as additional kernel development resources.
@@ Line 431: / Line 431: @@
 : Network interfaces are capable of communication across a network and are generally hardware devices, such as the "MACB" controller on Atmel hardware or a NIC on a PC. A network interface driver handles packet transmission, and identifies each device with a unique name on the system, such as <code>eth0</code>.
-The Linux kernel device driver system implements a layered approach. This means that specific devices are separated into subsystems, which implement a common API and share core code between all drivers. Using this approach speeds development time and maintenance, ensures a common interface, and encourages code reuse among other benefits.
+The Linux kernel device driver system implements a layered approach. This means that specific devices are separated into subsystems, which implement a common API and share core code between all drivers.  Among other benefits, using this approach speeds development time and maintenance, ensures a common interface, and encourages code reuse.
 A simple example of the driver model is the SPI subsystem, which provides a core SPI API with support for SPI controller drivers and SPI protocol drivers. Controller drivers provide direct access to the hardware, transmitting and receiving data on the physical pins. Protocol drivers pass messages through the controller driver to communicate with other devices using a specific protocol. Kernel and userlevel APIs are provided for initializing, declaring, and accessing SPI devices. Creating a new SPI controller driver is a matter of providing code to support the functions required by the SPI controller core that behave as specified and registering the driver during initialization. See <code>Documentation/spi/</code>, <code>drivers/spi/</code>, and <code>include/linux/spi/</code> to examine this structure.
@@ Line 437: / Line 437: @@
 === Driver Development Process ===
-The first steps in developing or expanding a driver for a particular device include obtaining information about the device and determining what drivers already exist for this device or similar devices. This process may start through Internet searches, requesting information from the manufacturer, and searching through the kernel source as well as the source for the most recent kernels on the Kernel.org site. Review of any existing drivers should provide a good idea of where your driver should fall in the kernel, what APIs it should use, and it's basic structure. Depending on the device there may be several valid options which will need to be evaluated based on the needs of the application.
+The first steps in developing or expanding a driver for a particular device include obtaining information about the device and determining what drivers already exist for this device or similar devices. This process may start through Internet searches, requesting information from the manufacturer, and searching through the kernel source as well as the source for the most recent kernels on the [http://kernel.org/ kernel.org] site. Review of any existing drivers should provide a good idea of where your driver should fall in the kernel, what APIs it should use, and its basic structure. Depending on the device there may be several valid options which will need to be evaluated based on the needs of the application.
 Once the location and structure of the driver have been decided, the code may be implemented. Several points should be considered as part of the driver development:
@@ Line 466: / Line 466: @@
 ; ''Linux Device Drivers, Third Edition'' (LDD3)
 : This book is available online in free PDF form through the [http://lwn.net/Kernel/LDD3 LWN.net site]. It is also available in-print through O'Reilly. LDD3 covers most of the topics required for Linux kernel development and includes examples. Note that some of the APIs covered have changed since 2.6.10 when the book was written so adaptation may be required to use the example code.
 ; Mailing Lists
 : There are many very active mailing lists (see http://vger.kernel.org/vger-lists.html) that can be used to ask questions or search through archives for solutions. The archive of the Linux Kernel mailing list is available at [https://lkml.org/ LKML.org] and archives to other lists can be found through a web search as well as links noted in the list [http://vger.kernel.org/vger-lists.html here].