Input: update some documentation
Input-programming.txt got out of sync with the latest changes in input
core; let's refresh it.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/Documentation/input/input-programming.txt b/Documentation/input/input-programming.txt
index 180e0689..d9d5230 100644
--- a/Documentation/input/input-programming.txt
+++ b/Documentation/input/input-programming.txt
@@ -1,5 +1,3 @@
-$Id: input-programming.txt,v 1.4 2001/05/04 09:47:14 vojtech Exp $
-
Programming input drivers
~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -20,28 +18,51 @@
#include <asm/irq.h>
#include <asm/io.h>
+static struct input_dev *button_dev;
+
static void button_interrupt(int irq, void *dummy, struct pt_regs *fp)
{
- input_report_key(&button_dev, BTN_1, inb(BUTTON_PORT) & 1);
- input_sync(&button_dev);
+ input_report_key(button_dev, BTN_1, inb(BUTTON_PORT) & 1);
+ input_sync(button_dev);
}
static int __init button_init(void)
{
+ int error;
+
if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) {
printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq);
return -EBUSY;
}
-
- button_dev.evbit[0] = BIT(EV_KEY);
- button_dev.keybit[LONG(BTN_0)] = BIT(BTN_0);
-
- input_register_device(&button_dev);
+
+ button_dev = input_allocate_device();
+ if (!button_dev) {
+ printk(KERN_ERR "button.c: Not enough memory\n");
+ error = -ENOMEM;
+ goto err_free_irq;
+ }
+
+ button_dev->evbit[0] = BIT(EV_KEY);
+ button_dev->keybit[LONG(BTN_0)] = BIT(BTN_0);
+
+ error = input_register_device(button_dev);
+ if (error) {
+ printk(KERN_ERR "button.c: Failed to register device\n");
+ goto err_free_dev;
+ }
+
+ return 0;
+
+ err_free_dev:
+ input_free_device(button_dev);
+ err_free_irq:
+ free_irq(BUTTON_IRQ, button_interrupt);
+ return error;
}
static void __exit button_exit(void)
{
- input_unregister_device(&button_dev);
+ input_unregister_device(button_dev);
free_irq(BUTTON_IRQ, button_interrupt);
}
@@ -58,17 +79,18 @@
booting the kernel, it grabs the required resources (it should also check
for the presence of the device).
-Then it sets the input bitfields. This way the device driver tells the other
+Then it allocates a new input device structure with input_aloocate_device()
+and sets up input bitfields. This way the device driver tells the other
parts of the input systems what it is - what events can be generated or
-accepted by this input device. Our example device can only generate EV_KEY type
-events, and from those only BTN_0 event code. Thus we only set these two
-bits. We could have used
+accepted by this input device. Our example device can only generate EV_KEY
+type events, and from those only BTN_0 event code. Thus we only set these
+two bits. We could have used
set_bit(EV_KEY, button_dev.evbit);
set_bit(BTN_0, button_dev.keybit);
as well, but with more than single bits the first approach tends to be
-shorter.
+shorter.
Then the example driver registers the input device structure by calling
@@ -76,16 +98,15 @@
This adds the button_dev structure to linked lists of the input driver and
calls device handler modules _connect functions to tell them a new input
-device has appeared. Because the _connect functions may call kmalloc(,
-GFP_KERNEL), which can sleep, input_register_device() must not be called
-from an interrupt or with a spinlock held.
+device has appeared. input_register_device() may sleep and therefore must
+not be called from an interrupt or with a spinlock held.
While in use, the only used function of the driver is
button_interrupt()
which upon every interrupt from the button checks its state and reports it
-via the
+via the
input_report_key()
@@ -113,16 +134,10 @@
release the interrupt and when it must resume polling or grab the interrupt
again. To do that, we would add this to our example driver:
-int button_used = 0;
-
static int button_open(struct input_dev *dev)
{
- if (button_used++)
- return 0;
-
if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) {
printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq);
- button_used--;
return -EBUSY;
}
@@ -131,20 +146,21 @@
static void button_close(struct input_dev *dev)
{
- if (!--button_used)
- free_irq(IRQ_AMIGA_VERTB, button_interrupt);
+ free_irq(IRQ_AMIGA_VERTB, button_interrupt);
}
static int __init button_init(void)
{
...
- button_dev.open = button_open;
- button_dev.close = button_close;
+ button_dev->open = button_open;
+ button_dev->close = button_close;
...
}
-Note the button_used variable - we have to track how many times the open
-function was called to know when exactly our device stops being used.
+Note that input core keeps track of number of users for the device and
+makes sure that dev->open() is called only when the first user connects
+to the device and that dev->close() is called when the very last user
+disconnects. Calls to both callbacks are serialized.
The open() callback should return a 0 in case of success or any nonzero value
in case of failure. The close() callback (which is void) must always succeed.
@@ -175,7 +191,7 @@
input_report_rel(struct input_dev *dev, int code, int value)
-function. Events are generated only for nonzero value.
+function. Events are generated only for nonzero value.
However EV_ABS requires a little special care. Before calling
input_register_device, you have to fill additional fields in the input_dev
@@ -187,6 +203,10 @@
button_dev.absfuzz[ABS_X] = 4;
button_dev.absflat[ABS_X] = 8;
+Or, you can just say:
+
+ input_set_abs_params(button_dev, ABS_X, 0, 255, 4, 8);
+
This setting would be appropriate for a joystick X axis, with the minimum of
0, maximum of 255 (which the joystick *must* be able to reach, no problem if
it sometimes reports more, but it must be able to always reach the min and
@@ -197,14 +217,7 @@
that the thing is precise and always returns to exactly the center position
(if it has any).
-1.4 The void *private field
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-This field in the input structure can be used to point to any private data
-structures in the input device driver, in case the driver handles more than
-one device. You'll need it in the open and close callbacks.
-
-1.5 NBITS(), LONG(), BIT()
+1.4 NBITS(), LONG(), BIT()
~~~~~~~~~~~~~~~~~~~~~~~~~~
These three macros from input.h help some bitfield computations:
@@ -213,13 +226,9 @@
LONG(x) - returns the index in the array in longs for bit x
BIT(x) - returns the index in a long for bit x
-1.6 The number, id* and name fields
+1.5 The id* and name fields
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The dev->number is assigned by the input system to the input device when it
-is registered. It has no use except for identifying the device to the user
-in system messages.
-
The dev->name should be set before registering the input device by the input
device driver. It's a string like 'Generic button device' containing a
user friendly name of the device.
@@ -234,15 +243,25 @@
The id and name fields can be passed to userland via the evdev interface.
-1.7 The keycode, keycodemax, keycodesize fields
+1.6 The keycode, keycodemax, keycodesize fields
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-These two fields will be used for any input devices that report their data
-as scancodes. If not all scancodes can be known by autodetection, they may
-need to be set by userland utilities. The keycode array then is an array
-used to map from scancodes to input system keycodes. The keycode max will
-contain the size of the array and keycodesize the size of each entry in it
-(in bytes).
+These three fields should be used by input devices that have dense keymaps.
+The keycode is an array used to map from scancodes to input system keycodes.
+The keycode max should contain the size of the array and keycodesize the
+size of each entry in it (in bytes).
+
+Userspace can query and alter current scancode to keycode mappings using
+EVIOCGKEYCODE and EVIOCSKEYCODE ioctls on corresponding evdev interface.
+When a device has all 3 aforementioned fields filled in, the driver may
+rely on kernel's default implementation of setting and querying keycode
+mappings.
+
+1.7 dev->getkeycode() and dev->setkeycode()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+getkeycode() and setkeycode() callbacks allow drivers to override default
+keycode/keycodesize/keycodemax mapping mechanism provided by input core
+and implement sparse keycode maps.
1.8 Key autorepeat
~~~~~~~~~~~~~~~~~~
@@ -266,7 +285,7 @@
driver can handle these events, it has to set the respective bits in evbit,
*and* also the callback routine:
- button_dev.event = button_event;
+ button_dev->event = button_event;
int button_event(struct input_dev *dev, unsigned int type, unsigned int code, int value);
{