1 files changed, 28 insertions, 7 deletions

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 2ee6c7a68bd..cd323254ca6 100644
--- 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);