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- <title>V4L2 Driver Programming</title>
-
- <!-- This part defines the interface between the "videodev"
- module and individual drivers. -->
-
- <para>to do</para>
-<!--
- <para>V4L2 is a two-layer driver system. The top layer is the "videodev"
-kernel module. When videodev initializes it registers as character device
-with major number 81, and it registers a set of file operations. All V4L2
-drivers are really clients of videodev, which calls V4L2 drivers through
-driver method functions. V4L2 drivers are also written as kernel modules.
-After probing the hardware they register one or more devices with
-videodev.</para>
-
- <section id="driver-modules">
- <title>Driver Modules</title>
-
- <para>V4L2 driver modules must have an initialization function which is
-called after the module was loaded into kernel, an exit function whis is
-called before the module is removed. When the driver is compiled into the
-kernel these functions called at system boot and shutdown time.</para>
-
- <informalexample>
- <programlisting>
-#include &lt;linux/module.h&gt;
-
-/* Export information about this module. For details and other useful
- macros see <filename>linux/module.h</filename>. */
-MODULE_DESCRIPTION("my - driver for my hardware");
-MODULE_AUTHOR("Your name here");
-MODULE_LICENSE("GPL");
-
-static void
-my_module_exit (void)
-{
- /* Free all resources allocated by my_module_init(). */
-}
-
-static int
-my_module_init (void)
-{
- /* Bind the driver to the supported hardware, see
- <link linkend="driver-pci"> and
- <link linkend="driver-usb"> for examples. */
-
- return 0; /* a negative value on error, 0 on success. */
-}
-
-/* Export module functions. */
-module_init (my_module_init);
-module_exit (my_module_exit);
-</programlisting>
- </informalexample>
-
- <para>Users can add parameters when kernel modules are inserted:</para>
-
- <informalexample>
- <programlisting>
-include &lt;linux/moduleparam.h&gt;
-
-static int my_option = 123;
-static int my_option_array[47];
-
-/* Export the symbol, an int, with access permissions 0664.
- See <filename>linux/moduleparam.h</filename> for other types. */
-module_param (my_option, int, 0644);
-module_param_array (my_option_array, int, NULL, 0644);
-
-MODULE_PARM_DESC (my_option, "Does magic things, default 123");
-</programlisting>
- </informalexample>
-
- <para>One parameter should be supported by all V4L2 drivers, the minor
-number of the device it will register. Purpose is to predictably link V4L2
-drivers to device nodes if more than one video device is installed. Use the
-name of the device node followed by a "_nr" suffix, for example "video_nr"
-for <filename>/dev/video</filename>.</para>
-
- <informalexample>
- <programlisting>
-/* Minor number of the device, -1 to allocate the first unused. */
-static int video_nr = -1;
-
-module_param (video_nr, int, 0444);
-</programlisting>
- </informalexample>
- </section>
-
- <section id="driver-pci">
- <title>PCI Devices</title>
-
- <para>PCI devices are initialized like this:</para>
-
- <informalexample>
- <programlisting>
-typedef struct {
- /* State of one physical device. */
-} my_device;
-
-static int
-my_resume (struct pci_dev * pci_dev)
-{
- /* Restore the suspended device to working state. */
-}
-
-static int
-my_suspend (struct pci_dev * pci_dev,
- pm_message_t state)
-{
- /* This function is called before the system goes to sleep.
- Stop all DMAs and disable interrupts, then put the device
- into a low power state. For details see the kernel
- sources under <filename>Documentation/power</filename>. */
-
- return 0; /* a negative value on error, 0 on success. */
-}
-
-static void __devexit
-my_remove (struct pci_dev * pci_dev)
-{
- my_device *my = pci_get_drvdata (pci_dev);
-
- /* Describe me. */
-}
-
-static int __devinit
-my_probe (struct pci_dev * pci_dev,
- const struct pci_device_id * pci_id)
-{
- my_device *my;
-
- /* Describe me. */
-
- /* You can allocate per-device data here and store a pointer
- to it in the pci_dev structure. */
- my = ...;
- pci_set_drvdata (pci_dev, my);
-
- return 0; /* a negative value on error, 0 on success. */
-}
-
-/* A list of supported PCI devices. */
-static struct pci_device_id
-my_pci_device_ids [] = {
- { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR,
- PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
- { 0 } /* end of list */
-};
-
-/* Load our module if supported PCI devices are installed. */
-MODULE_DEVICE_TABLE (pci, my_pci_device_ids);
-
-static struct pci_driver
-my_pci_driver = {
- .name = "my",
- .id_table = my_pci_device_ids,
-
- .probe = my_probe,
- .remove = __devexit_p (my_remove),
-
- /* Power management functions. */
- .suspend = my_suspend,
- .resume = my_resume,
-};
-
-static void
-my_module_exit (void)
-{
- pci_unregister_driver (&my_pci_driver);
-}
-
-static int
-my_module_init (void)
-{
- return pci_register_driver (&my_pci_driver);
-}
-</programlisting>
- </informalexample>
- </section>
-
- <section id="driver-usb">
- <title>USB Devices</title>
- <para>to do</para>
- </section>
- <section id="driver-registering">
- <title>Registering V4L2 Drivers</title>
-
- <para>After a V4L2 driver probed the hardware it registers one or more
-devices with the videodev module.</para>
- </section>
- <section id="driver-file-ops">
- <title>File Operations</title>
- <para>to do</para>
- </section>
- <section id="driver-internal-api">
- <title>Internal API</title>
- <para>to do</para>
- </section>
--->