static ssize_t
printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
struct printer_dev *dev = fd->private_data;
unsigned long flags;
size_t size;
size_t bytes_copied;
struct usb_request *req;
/* This is a pointer to the current USB rx request. */
struct usb_request *current_rx_req;
/* This is the number of bytes in the current rx buffer. */
size_t current_rx_bytes;
/* This is a pointer to the current rx buffer. */
u8 *current_rx_buf;
if (len == 0)
return -EINVAL;
DBG(dev, "printer_read trying to read %d bytes\n", (int)len);
mutex_lock(&dev->lock_printer_io);
spin_lock_irqsave(&dev->lock, flags);
/* We will use this flag later to check if a printer reset happened
* after we turn interrupts back on.
*/
dev->reset_printer = 0;
setup_rx_reqs(dev);
bytes_copied = 0;
current_rx_req = dev->current_rx_req;
current_rx_bytes = dev->current_rx_bytes;
current_rx_buf = dev->current_rx_buf;
dev->current_rx_req = NULL;
dev->current_rx_bytes = 0;
dev->current_rx_buf = NULL;
/* Check if there is any data in the read buffers. Please note that
* current_rx_bytes is the number of bytes in the current rx buffer.
* If it is zero then check if there are any other rx_buffers that
* are on the completed list. We are only out of data if all rx
* buffers are empty.
*/
if ((current_rx_bytes == 0) &&
(likely(list_empty(&dev->rx_buffers)))) {
/* Turn interrupts back on before sleeping. */
spin_unlock_irqrestore(&dev->lock, flags);
/*
* If no data is available check if this is a NON-Blocking
* call or not.
*/
if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
mutex_unlock(&dev->lock_printer_io);
return -EAGAIN;
}
/* Sleep until data is available */
wait_event_interruptible(dev->rx_wait,
(likely(!list_empty(&dev->rx_buffers))));
spin_lock_irqsave(&dev->lock, flags);
}
/* We have data to return then copy it to the caller's buffer.*/
while ((current_rx_bytes || likely(!list_empty(&dev->rx_buffers)))
&& len) {
if (current_rx_bytes == 0) {
req = container_of(dev->rx_buffers.next,
struct usb_request, list);
list_del_init(&req->list);
if (req->actual && req->buf) {
current_rx_req = req;
current_rx_bytes = req->actual;
current_rx_buf = req->buf;
} else {
list_add(&req->list, &dev->rx_reqs);
continue;
}
}
/* Don't leave irqs off while doing memory copies */
spin_unlock_irqrestore(&dev->lock, flags);
if (len > current_rx_bytes)
size = current_rx_bytes;
else
size = len;
size -= copy_to_user(buf, current_rx_buf, size);
bytes_copied += size;
len -= size;
buf += size;
spin_lock_irqsave(&dev->lock, flags);
/* We've disconnected or reset so return. */
if (dev->reset_printer) {
list_add(¤t_rx_req->list, &dev->rx_reqs);
spin_unlock_irqrestore(&dev->lock, flags);
mutex_unlock(&dev->lock_printer_io);
return -EAGAIN;
}
/* If we not returning all the data left in this RX request
* buffer then adjust the amount of data left in the buffer.
* Othewise if we are done with this RX request buffer then
* requeue it to get any incoming data from the USB host.
*/
if (size < current_rx_bytes) {
current_rx_bytes -= size;
current_rx_buf += size;
} else {
list_add(¤t_rx_req->list, &dev->rx_reqs);
current_rx_bytes = 0;
current_rx_buf = NULL;
current_rx_req = NULL;
}
}
static ssize_t
printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
struct printer_dev *dev = fd->private_data;
unsigned long flags;
size_t size;
size_t bytes_copied;
struct usb_request *req;
struct usb_request *current_rx_req;
size_t current_rx_bytes;
u8 *current_rx_buf;
if (len == 0)
return -EINVAL;
DBG(dev, "printer_read trying to read %d bytes\n", (int)len);
mutex_lock(&dev->lock_printer_io);
spin_lock_irqsave(&dev->lock, flags);
dev->reset_printer = 0;
setup_rx_reqs(dev);
bytes_copied = 0;
current_rx_req = dev->current_rx_req;
current_rx_bytes = dev->current_rx_bytes;
current_rx_buf = dev->current_rx_buf;
dev->current_rx_req = NULL;
dev->current_rx_bytes = 0;
dev->current_rx_buf = NULL;
if ((current_rx_bytes == 0) &&
(likely(list_empty(&dev->rx_buffers)))) {
spin_unlock_irqrestore(&dev->lock, flags);
if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
mutex_unlock(&dev->lock_printer_io);
return -EAGAIN;
}
wait_event_interruptible(dev->rx_wait,
(likely(!list_empty(&dev->rx_buffers))));
spin_lock_irqsave(&dev->lock, flags);
}
while ((current_rx_bytes || likely(!list_empty(&dev->rx_buffers)))
&& len) {
if (current_rx_bytes == 0) {
req = container_of(dev->rx_buffers.next,
struct usb_request, list);
list_del_init(&req->list);
if (req->actual && req->buf) {
current_rx_req = req;
current_rx_bytes = req->actual;
current_rx_buf = req->buf;
} else {
list_add(&req->list, &dev->rx_reqs);
continue;
}
}
spin_unlock_irqrestore(&dev->lock, flags);
if (len > current_rx_bytes)
size = current_rx_bytes;
else
size = len;
size -= copy_to_user(buf, current_rx_buf, size);
bytes_copied += size;
len -= size;
buf += size;
spin_lock_irqsave(&dev->lock, flags);
if (dev->reset_printer) {
list_add(¤t_rx_req->list, &dev->rx_reqs);
spin_unlock_irqrestore(&dev->lock, flags);
mutex_unlock(&dev->lock_printer_io);
return -EAGAIN;
}
if (size < current_rx_bytes) {
current_rx_bytes -= size;
current_rx_buf += size;
} else {
list_add(¤t_rx_req->list, &dev->rx_reqs);
current_rx_bytes = 0;
current_rx_buf = NULL;
current_rx_req = NULL;
}
}
