Input: evdev - never leave the client buffer empty after write

[deliverable/linux.git] / drivers / input / evdev.c

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 2ee6c7a68bdccf4c9cf6c330f824d341f0a69302..cd323254ca6f560a1b7d38b5283297f67f5b84ee 100644 (file)
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -10,7 +10,8 @@
 
 #define EVDEV_MINOR_BASE       64
 #define EVDEV_MINORS           32
-#define EVDEV_BUFFER_SIZE      64
+#define EVDEV_MIN_BUFFER_SIZE  64U
+#define EVDEV_BUF_PACKETS      8
 
 #include <linux/poll.h>
 #include <linux/sched.h>
@@ -36,13 +37,14 @@ struct evdev {
 };
 
 struct evdev_client {
-       struct input_event buffer[EVDEV_BUFFER_SIZE];
        int head;
        int tail;
        spinlock_t buffer_lock; /* protects access to buffer, head and tail */
        struct fasync_struct *fasync;
        struct evdev *evdev;
        struct list_head node;
+       int bufsize;
+       struct input_event buffer[];
 };
 
 static struct evdev *evdev_table[EVDEV_MINORS];
@@ -52,11 +54,15 @@ static void evdev_pass_event(struct evdev_client *client,
                             struct input_event *event)
 {
        /*
-        * Interrupts are disabled, just acquire the lock
+        * Interrupts are disabled, just acquire the lock.
+        * Make sure we don't leave with the client buffer
+        * "empty" by having client->head == client->tail.
         */
        spin_lock(&client->buffer_lock);
-       client->buffer[client->head++] = *event;
-       client->head &= EVDEV_BUFFER_SIZE - 1;
+       do {
+               client->buffer[client->head++] = *event;
+               client->head &= client->bufsize - 1;
+       } while (client->head == client->tail);
        spin_unlock(&client->buffer_lock);
 
        if (event->type == EV_SYN)
@@ -242,11 +248,21 @@ static int evdev_release(struct inode *inode, struct file *file)
        return 0;
 }
 
+static unsigned int evdev_compute_buffer_size(struct input_dev *dev)
+{
+       unsigned int n_events =
+               max(dev->hint_events_per_packet * EVDEV_BUF_PACKETS,
+                   EVDEV_MIN_BUFFER_SIZE);
+
+       return roundup_pow_of_two(n_events);
+}
+
 static int evdev_open(struct inode *inode, struct file *file)
 {
        struct evdev *evdev;
        struct evdev_client *client;
        int i = iminor(inode) - EVDEV_MINOR_BASE;
+       unsigned int bufsize;
        int error;
 
        if (i >= EVDEV_MINORS)
@@ -263,12 +279,17 @@ static int evdev_open(struct inode *inode, struct file *file)
        if (!evdev)
                return -ENODEV;
 
-       client = kzalloc(sizeof(struct evdev_client), GFP_KERNEL);
+       bufsize = evdev_compute_buffer_size(evdev->handle.dev);
+
+       client = kzalloc(sizeof(struct evdev_client) +
+                               bufsize * sizeof(struct input_event),
+                        GFP_KERNEL);
        if (!client) {
                error = -ENOMEM;
                goto err_put_evdev;
        }
 
+       client->bufsize = bufsize;
        spin_lock_init(&client->buffer_lock);
        client->evdev = evdev;
        evdev_attach_client(evdev, client);
@@ -334,7 +355,7 @@ static int evdev_fetch_next_event(struct evdev_client *client,
        have_event = client->head != client->tail;
        if (have_event) {
                *event = client->buffer[client->tail++];
-               client->tail &= EVDEV_BUFFER_SIZE - 1;
+               client->tail &= client->bufsize - 1;
        }
 
        spin_unlock_irq(&client->buffer_lock);