diff options
Diffstat (limited to 'drivers/usb/class/cdc-wdm.c')
| -rw-r--r-- | drivers/usb/class/cdc-wdm.c | 103 |
1 files changed, 4 insertions, 99 deletions
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c index 8fda45a45bd3..08669fee6d7f 100644 --- a/drivers/usb/class/cdc-wdm.c +++ b/drivers/usb/class/cdc-wdm.c @@ -58,7 +58,6 @@ MODULE_DEVICE_TABLE (usb, wdm_ids); #define WDM_SUSPENDING 8 #define WDM_RESETTING 9 #define WDM_OVERFLOW 10 -#define WDM_DRAIN_ON_OPEN 11 #define WDM_MAX 16 @@ -182,7 +181,7 @@ static void wdm_in_callback(struct urb *urb) "nonzero urb status received: -ESHUTDOWN\n"); goto skip_error; case -EPIPE: - dev_dbg(&desc->intf->dev, + dev_err(&desc->intf->dev, "nonzero urb status received: -EPIPE\n"); break; default: @@ -210,25 +209,6 @@ static void wdm_in_callback(struct urb *urb) desc->reslength = length; } } - - /* - * Handling devices with the WDM_DRAIN_ON_OPEN flag set: - * If desc->resp_count is unset, then the urb was submitted - * without a prior notification. If the device returned any - * data, then this implies that it had messages queued without - * notifying us. Continue reading until that queue is flushed. - */ - if (!desc->resp_count) { - if (!length) { - /* do not propagate the expected -EPIPE */ - desc->rerr = 0; - goto unlock; - } - dev_dbg(&desc->intf->dev, "got %d bytes without notification\n", length); - set_bit(WDM_RESPONDING, &desc->flags); - usb_submit_urb(desc->response, GFP_ATOMIC); - } - skip_error: set_bit(WDM_READ, &desc->flags); wake_up(&desc->wait); @@ -243,7 +223,6 @@ skip_error: service_outstanding_interrupt(desc); } -unlock: spin_unlock(&desc->iuspin); } @@ -686,17 +665,6 @@ static int wdm_open(struct inode *inode, struct file *file) dev_err(&desc->intf->dev, "Error submitting int urb - %d\n", rv); rv = usb_translate_errors(rv); - } else if (test_bit(WDM_DRAIN_ON_OPEN, &desc->flags)) { - /* - * Some devices keep pending messages queued - * without resending notifications. We must - * flush the message queue before we can - * assume a one-to-one relationship between - * notifications and messages in the queue - */ - dev_dbg(&desc->intf->dev, "draining queued data\n"); - set_bit(WDM_RESPONDING, &desc->flags); - rv = usb_submit_urb(desc->response, GFP_KERNEL); } } else { rv = 0; @@ -803,8 +771,7 @@ static void wdm_rxwork(struct work_struct *work) /* --- hotplug --- */ static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor *ep, - u16 bufsize, int (*manage_power)(struct usb_interface *, int), - bool drain_on_open) + u16 bufsize, int (*manage_power)(struct usb_interface *, int)) { int rv = -ENOMEM; struct wdm_device *desc; @@ -891,68 +858,6 @@ static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor desc->manage_power = manage_power; - /* - * "drain_on_open" enables a hack to work around a firmware - * issue observed on network functions, in particular MBIM - * functions. - * - * Quoting section 7 of the CDC-WMC r1.1 specification: - * - * "The firmware shall interpret GetEncapsulatedResponse as a - * request to read response bytes. The firmware shall send - * the next wLength bytes from the response. The firmware - * shall allow the host to retrieve data using any number of - * GetEncapsulatedResponse requests. The firmware shall - * return a zero- length reply if there are no data bytes - * available. - * - * The firmware shall send ResponseAvailable notifications - * periodically, using any appropriate algorithm, to inform - * the host that there is data available in the reply - * buffer. The firmware is allowed to send ResponseAvailable - * notifications even if there is no data available, but - * this will obviously reduce overall performance." - * - * These requirements, although they make equally sense, are - * often not implemented by network functions. Some firmwares - * will queue data indefinitely, without ever resending a - * notification. The result is that the driver and firmware - * loses "syncronization" if the driver ever fails to respond - * to a single notification, something which easily can happen - * on release(). When this happens, the driver will appear to - * never receive notifications for the most current data. Each - * notification will only cause a single read, which returns - * the oldest data in the firmware's queue. - * - * The "drain_on_open" hack resolves the situation by draining - * data from the firmware until none is returned, without a - * prior notification. - * - * This will inevitably race with the firmware, risking that - * we read data from the device before handling the associated - * notification. To make things worse, some of the devices - * needing the hack do not implement the "return zero if no - * data is available" requirement either. Instead they return - * an error on the subsequent read in this case. This means - * that "winning" the race can cause an unexpected EIO to - * userspace. - * - * "winning" the race is more likely on resume() than on - * open(), and the unexpected error is more harmful in the - * middle of an open session. The hack is therefore only - * applied on open(), and not on resume() where it logically - * would be equally necessary. So we define open() as the only - * driver <-> device "syncronization point". Should we happen - * to lose a notification after open(), then syncronization - * will be lost until release() - * - * The hack should not be enabled for CDC WDM devices - * conforming to the CDC-WMC r1.1 specification. This is - * ensured by setting drain_on_open to false in wdm_probe(). - */ - if (drain_on_open) - set_bit(WDM_DRAIN_ON_OPEN, &desc->flags); - spin_lock(&wdm_device_list_lock); list_add(&desc->device_list, &wdm_device_list); spin_unlock(&wdm_device_list_lock); @@ -1006,7 +911,7 @@ static int wdm_probe(struct usb_interface *intf, const struct usb_device_id *id) goto err; ep = &iface->endpoint[0].desc; - rv = wdm_create(intf, ep, maxcom, &wdm_manage_power, false); + rv = wdm_create(intf, ep, maxcom, &wdm_manage_power); err: return rv; @@ -1038,7 +943,7 @@ struct usb_driver *usb_cdc_wdm_register(struct usb_interface *intf, { int rv = -EINVAL; - rv = wdm_create(intf, ep, bufsize, manage_power, true); + rv = wdm_create(intf, ep, bufsize, manage_power); if (rv < 0) goto err; |