User GPIO Driver - Revision history

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2010-11-23T23:26:31Z

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Aqisecoxefi at 22:44, 23 November 2010

2010-11-23T22:44:47Z

Dhylands: Added instructions for building under OE

2010-02-18T17:29:32Z

Added instructions for building under OE

Dhylands: Initial version of user-gpio driver page

2010-02-11T20:45:25Z

Initial version of user-gpio driver page

New page

This page documents the user GPIO driver, which is a reflection of the kernel's gpiolib API into user space.

==Overview==

The kernel provides an API, called gpiolib, which abstracts access to GPIO pins. It has a mechanism for exporting pins into userspace, and in general this is the preferred method of accessing gpio pins from userspace. This method works particularly well if it is setup for a given overo/daughtercard combination. However, since the kernel is often configured in a more generic manner, using the export method is inconvenient, so the user-gpio driver was created.

WARNING: It is possible to damage your overo chip if you do things incorrectly. This code has no way of knowing for example, if a pin is physically connected to an output or not. If, for example, a GPIO pin was connected to Vcc, and you choose to configure that pin as an output and drive it low, you've essentially created a short circuit, and this can stress or damagethe pin, possibly bricking your processor. You have been warned.

== Driver Sources ==

The source code can be found [http://svn.hylands.org/linux/gpio/ here]. The app directory contains the example user mode application. The lib directory contains the usermode library which translates the C API into the appropriate ioctl calls into the kernel driver, and the module directory contains the loadable kernel module. The Makefiles have been setup such that if you define the environment variable OVEROTOP then you should be able to just type make in top level directory and both the app and module will be built.

There are also some bitbake recipes in the [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-app gpio-app], [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-lib gpio-lib] and [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-event-module gpio-event-module] directories.

[[Category: GPIO]]

@@ Line 1: / Line 1: @@
 This page documents the user GPIO driver, which is a reflection of the kernel's gpiolib API into user space.
@@ Line 24: / Line 16: @@
 In order to build the driver under OE, you can do the following:
-&lt;pre&gt;
+<pre>
   cd to the directory containing org.embedded.dev
   svn co http://svn.hylands.org/linux/oe/user.collection user.collection
   bitbake task-gpio-all
-&lt;/pre&gt;
+</pre>
 This will build the following packages for the [[GPIO Event Driver]]:

@@ Line 1: / Line 1: @@
 This page documents the user GPIO driver, which is a reflection of the kernel's gpiolib API into user space.
@@ Line 16: / Line 24: @@
 In order to build the driver under OE, you can do the following:
-<pre>
+&lt;pre&gt;
   cd to the directory containing org.embedded.dev
   svn co http://svn.hylands.org/linux/oe/user.collection user.collection
   bitbake task-gpio-all
-</pre>
+&lt;/pre&gt;
 This will build the following packages for the [[GPIO Event Driver]]:

← Older revision		Revision as of 17:29, 18 February 2010
Line 12:		Line 12:

	There are also some bitbake recipes in the [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-app gpio-app], [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-lib gpio-lib] and [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-event-module gpio-event-module] directories.		There are also some bitbake recipes in the [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-app gpio-app], [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-lib gpio-lib] and [http://svn.hylands.org/linux/oe/user.collection/recipes/gpio-event-module gpio-event-module] directories.
		+
		+	== Integrating/Building with Open Embedded ==
		+
		+	In order to build the driver under OE, you can do the following:
		+	<pre>
		+	cd to the directory containing org.embedded.dev
		+	svn co http://svn.hylands.org/linux/oe/user.collection user.collection
		+	bitbake task-gpio-all
		+	</pre>
		+
		+	This will build the following packages for the [[GPIO Event Driver]]:
		+	./deploy/glibc/ipk/overo/gpio-event-module_svn20100218-r50.5_overo.ipk
		+	./deploy/glibc/ipk/armv7a/gpio-event-app_svn20100218-r2.5_armv7a.ipk
		+
		+	and these packages for the user gpio driver:
		+	./deploy/glibc/ipk/overo/gpio-module_svn20100218-r50.5_overo.ipk
		+	./deploy/glibc/ipk/armv7a/gpio-app_svn20100218-r0.5_armv7a.ipk
		+	./deploy/glibc/ipk/armv7a/gpio-lib_svn20100218-r0.5_armv7a.ipk
		+
		+	Note that the numeric portions of the pathnames will almost certainly be different.

	[[Category: GPIO]]		[[Category: GPIO]]