According to the standard count 0 is special - no IO should happen but we
can check error conditions (device gone away, etc), and return 0 if there
are no errors. We used to return -EINVAL instead and we also could return 0
if an event was "stolen: by another thread.
Signed-off-by: Dmitry Torokhov <dtor@xxxxxxx>
---
drivers/input/evdev.c | 54 +++++++++++++++++++++++++++++--------------------
1 files changed, 32 insertions(+), 22 deletions(-)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 8f59fc1..ff49ba3 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -346,7 +346,7 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer,
int written = 0;
int error;
- if (count < input_event_size())
+ if (count != 0 && count < input_event_size())
return -EINVAL;
error = mutex_lock_interruptible(&evdev->mutex);
@@ -358,7 +358,7 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer,
goto out;
}
- do {
+ while (written + input_event_size() <= count) {
if (input_event_from_user(buffer + written, &event)) {
error = -EFAULT;
goto out;
@@ -367,7 +367,7 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer,
input_inject_event(&evdev->handle,
event.type, event.code, event.value);
- } while (written + input_event_size() <= count);
+ }
out:
mutex_unlock(&evdev->mutex);
@@ -401,33 +401,43 @@ static ssize_t evdev_read(struct file *file, char __user *buffer,
int read = 0;
int error = 0;
- if (count < input_event_size())
+ if (count != 0 && count < input_event_size())
return -EINVAL;
- if (!(file->f_flags & O_NONBLOCK)) {
- error = wait_event_interruptible(evdev->wait,
- client->packet_head != client->tail ||
- !evdev->exist);
- if (error)
- return error;
- }
+ do {
+ if (!evdev->exist)
+ return -ENODEV;
- if (!evdev->exist)
- return -ENODEV;
+ if (client->packet_head == client->tail &&
+ (file->f_flags & O_NONBLOCK))
+ return -EAGAIN;
- while (read + input_event_size() <= count &&
- evdev_fetch_next_event(client, &event)) {
+ /*
+ * count == 0 is special - no IO is done but we check
+ * for error conditions.
+ */
+ if (count == 0)
+ break;
- if (input_event_to_user(buffer + read, &event)) {
- error = -EFAULT;
- goto out;
+ while (read + input_event_size() <= count &&
+ evdev_fetch_next_event(client, &event)) {
+
+ if (input_event_to_user(buffer + read, &event)) {
+ error = -EFAULT;
+ goto out;
+ }
+
+ read += input_event_size();
}
- read += input_event_size();
- }
+ if (read)
+ break;
- if (read == 0 && (file->f_flags & O_NONBLOCK))
- error = -EAGAIN;
+ if (!(file->f_flags & O_NONBLOCK))
+ error = wait_event_interruptible(evdev->wait,
+ client->packet_head != client->tail ||
+ !evdev->exist);
+ } while (!error);
out:
return read ?: error;
--
1.7.7.6
--
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