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Diffstat (limited to 'Documentation/usb')
| -rw-r--r-- | Documentation/usb/hiddev.txt | 205 |
1 files changed, 0 insertions, 205 deletions
diff --git a/Documentation/usb/hiddev.txt b/Documentation/usb/hiddev.txt deleted file mode 100644 index 6e8c9f1d2f22..000000000000 --- a/Documentation/usb/hiddev.txt +++ /dev/null @@ -1,205 +0,0 @@ -Care and feeding of your Human Interface Devices - -INTRODUCTION - -In addition to the normal input type HID devices, USB also uses the -human interface device protocols for things that are not really human -interfaces, but have similar sorts of communication needs. The two big -examples for this are power devices (especially uninterruptable power -supplies) and monitor control on higher end monitors. - -To support these disparate requirements, the Linux USB system provides -HID events to two separate interfaces: -* the input subsystem, which converts HID events into normal input -device interfaces (such as keyboard, mouse and joystick) and a -normalised event interface - see Documentation/input/input.txt -* the hiddev interface, which provides fairly raw HID events - -The data flow for a HID event produced by a device is something like -the following : - - usb.c ---> hid-core.c ----> hid-input.c ----> [keyboard/mouse/joystick/event] - | - | - --> hiddev.c ----> POWER / MONITOR CONTROL - -In addition, other subsystems (apart from USB) can potentially feed -events into the input subsystem, but these have no effect on the hid -device interface. - -USING THE HID DEVICE INTERFACE - -The hiddev interface is a char interface using the normal USB major, -with the minor numbers starting at 96 and finishing at 111. Therefore, -you need the following commands: -mknod /dev/usb/hiddev0 c 180 96 -mknod /dev/usb/hiddev1 c 180 97 -mknod /dev/usb/hiddev2 c 180 98 -mknod /dev/usb/hiddev3 c 180 99 -mknod /dev/usb/hiddev4 c 180 100 -mknod /dev/usb/hiddev5 c 180 101 -mknod /dev/usb/hiddev6 c 180 102 -mknod /dev/usb/hiddev7 c 180 103 -mknod /dev/usb/hiddev8 c 180 104 -mknod /dev/usb/hiddev9 c 180 105 -mknod /dev/usb/hiddev10 c 180 106 -mknod /dev/usb/hiddev11 c 180 107 -mknod /dev/usb/hiddev12 c 180 108 -mknod /dev/usb/hiddev13 c 180 109 -mknod /dev/usb/hiddev14 c 180 110 -mknod /dev/usb/hiddev15 c 180 111 - -So you point your hiddev compliant user-space program at the correct -interface for your device, and it all just works. - -Assuming that you have a hiddev compliant user-space program, of -course. If you need to write one, read on. - - -THE HIDDEV API -This description should be read in conjunction with the HID -specification, freely available from http://www.usb.org, and -conveniently linked of http://www.linux-usb.org. - -The hiddev API uses a read() interface, and a set of ioctl() calls. - -HID devices exchange data with the host computer using data -bundles called "reports". Each report is divided into "fields", -each of which can have one or more "usages". In the hid-core, -each one of these usages has a single signed 32 bit value. - -read(): -This is the event interface. When the HID device's state changes, -it performs an interrupt transfer containing a report which contains -the changed value. The hid-core.c module parses the report, and -returns to hiddev.c the individual usages that have changed within -the report. In its basic mode, the hiddev will make these individual -usage changes available to the reader using a struct hiddev_event: - - struct hiddev_event { - unsigned hid; - signed int value; - }; - -containing the HID usage identifier for the status that changed, and -the value that it was changed to. Note that the structure is defined -within <linux/hiddev.h>, along with some other useful #defines and -structures. The HID usage identifier is a composite of the HID usage -page shifted to the 16 high order bits ORed with the usage code. The -behavior of the read() function can be modified using the HIDIOCSFLAG -ioctl() described below. - - -ioctl(): -This is the control interface. There are a number of controls: - -HIDIOCGVERSION - int (read) -Gets the version code out of the hiddev driver. - -HIDIOCAPPLICATION - (none) -This ioctl call returns the HID application usage associated with the -hid device. The third argument to ioctl() specifies which application -index to get. This is useful when the device has more than one -application collection. If the index is invalid (greater or equal to -the number of application collections this device has) the ioctl -returns -1. You can find out beforehand how many application -collections the device has from the num_applications field from the -hiddev_devinfo structure. - -HIDIOCGCOLLECTIONINFO - struct hiddev_collection_info (read/write) -This returns a superset of the information above, providing not only -application collections, but all the collections the device has. It -also returns the level the collection lives in the hierarchy. -The user passes in a hiddev_collection_info struct with the index -field set to the index that should be returned. The ioctl fills in -the other fields. If the index is larger than the last collection -index, the ioctl returns -1 and sets errno to -EINVAL. - -HIDIOCGDEVINFO - struct hiddev_devinfo (read) -Gets a hiddev_devinfo structure which describes the device. - -HIDIOCGSTRING - struct hiddev_string_descriptor (read/write) -Gets a string descriptor from the device. The caller must fill in the -"index" field to indicate which descriptor should be returned. - -HIDIOCINITREPORT - (none) -Instructs the kernel to retrieve all input and feature report values -from the device. At this point, all the usage structures will contain -current values for the device, and will maintain it as the device -changes. Note that the use of this ioctl is unnecessary in general, -since later kernels automatically initialize the reports from the -device at attach time. - -HIDIOCGNAME - string (variable length) -Gets the device name - -HIDIOCGREPORT - struct hiddev_report_info (write) -Instructs the kernel to get a feature or input report from the device, -in order to selectively update the usage structures (in contrast to -INITREPORT). - -HIDIOCSREPORT - struct hiddev_report_info (write) -Instructs the kernel to send a report to the device. This report can -be filled in by the user through HIDIOCSUSAGE calls (below) to fill in -individual usage values in the report before sending the report in full -to the device. - -HIDIOCGREPORTINFO - struct hiddev_report_info (read/write) -Fills in a hiddev_report_info structure for the user. The report is -looked up by type (input, output or feature) and id, so these fields -must be filled in by the user. The ID can be absolute -- the actual -report id as reported by the device -- or relative -- -HID_REPORT_ID_FIRST for the first report, and (HID_REPORT_ID_NEXT | -report_id) for the next report after report_id. Without a-priori -information about report ids, the right way to use this ioctl is to -use the relative IDs above to enumerate the valid IDs. The ioctl -returns non-zero when there is no more next ID. The real report ID is -filled into the returned hiddev_report_info structure. - -HIDIOCGFIELDINFO - struct hiddev_field_info (read/write) -Returns the field information associated with a report in a -hiddev_field_info structure. The user must fill in report_id and -report_type in this structure, as above. The field_index should also -be filled in, which should be a number from 0 and maxfield-1, as -returned from a previous HIDIOCGREPORTINFO call. - -HIDIOCGUCODE - struct hiddev_usage_ref (read/write) -Returns the usage_code in a hiddev_usage_ref structure, given that -given its report type, report id, field index, and index within the -field have already been filled into the structure. - -HIDIOCGUSAGE - struct hiddev_usage_ref (read/write) -Returns the value of a usage in a hiddev_usage_ref structure. The -usage to be retrieved can be specified as above, or the user can -choose to fill in the report_type field and specify the report_id as -HID_REPORT_ID_UNKNOWN. In this case, the hiddev_usage_ref will be -filled in with the report and field information associated with this -usage if it is found. - -HIDIOCSUSAGE - struct hiddev_usage_ref (write) -Sets the value of a usage in an output report. The user fills in -the hiddev_usage_ref structure as above, but additionally fills in -the value field. - -HIDIOGCOLLECTIONINDEX - struct hiddev_usage_ref (write) -Returns the collection index associated with this usage. This -indicates where in the collection hierarchy this usage sits. - -HIDIOCGFLAG - int (read) -HIDIOCSFLAG - int (write) -These operations respectively inspect and replace the mode flags -that influence the read() call above. The flags are as follows: - - HIDDEV_FLAG_UREF - read() calls will now return - struct hiddev_usage_ref instead of struct hiddev_event. - This is a larger structure, but in situations where the - device has more than one usage in its reports with the - same usage code, this mode serves to resolve such - ambiguity. - - HIDDEV_FLAG_REPORT - This flag can only be used in conjunction - with HIDDEV_FLAG_UREF. With this flag set, when the device - sends a report, a struct hiddev_usage_ref will be returned - to read() filled in with the report_type and report_id, but - with field_index set to FIELD_INDEX_NONE. This serves as - additional notification when the device has sent a report. |