sysclk-lwla: Drain pending replies on initialization

[libsigrok.git] / src / hardware / sysclk-lwla / api.c

diff --git a/src/hardware/sysclk-lwla/api.c b/src/hardware/sysclk-lwla/api.c
index 7dfd7582f67c539219f199c2f2bebf9733977e34..e8c2cb0cdf359fc98f5d9ad2246d3f6d3361c9b7 100644 (file)
--- a/src/hardware/sysclk-lwla/api.c
+++ b/src/hardware/sysclk-lwla/api.c
@@ -248,6 +248,40 @@ static int dev_clear(const struct sr_dev_driver *di)
        return std_dev_clear(di, &clear_dev_context);
 }
 
+/* Drain any pending data from the USB transfer buffers on the device.
+ * This may be necessary e.g. after a crash or generally to clean up after
+ * an abnormal condition.
+ */
+static int drain_usb(struct sr_usb_dev_inst *usb, unsigned int endpoint)
+{
+       int drained, xfer_len;
+       int ret;
+       unsigned char buf[512];
+
+       const unsigned int drain_timeout_ms = 10;
+
+       drained = 0;
+       do {
+               xfer_len = 0;
+               ret = libusb_bulk_transfer(usb->devhdl, endpoint,
+                                          buf, sizeof buf, &xfer_len,
+                                          drain_timeout_ms);
+               drained += xfer_len;
+       } while (ret == LIBUSB_SUCCESS && xfer_len != 0);
+
+       if (ret != LIBUSB_SUCCESS && ret != LIBUSB_ERROR_TIMEOUT) {
+               sr_err("Failed to drain USB endpoint %u: %s.",
+                      endpoint & (LIBUSB_ENDPOINT_IN - 1),
+                      libusb_error_name(ret));
+               return SR_ERR;
+       }
+       if (drained > 0) {
+               sr_warn("Drained %d bytes from USB endpoint %u.",
+                       drained, endpoint & (LIBUSB_ENDPOINT_IN - 1));
+       }
+       return SR_OK;
+}
+
 /* Open and initialize device.
  */
 static int dev_open(struct sr_dev_inst *sdi)
@@ -275,7 +309,7 @@ static int dev_open(struct sr_dev_inst *sdi)
                return ret;
 
        ret = libusb_set_configuration(usb->devhdl, USB_CONFIG);
-       if (ret != 0) {
+       if (ret != LIBUSB_SUCCESS) {
                sr_err("Failed to set USB configuration: %s.",
                        libusb_error_name(ret));
                sr_usb_close(usb);
@@ -283,13 +317,17 @@ static int dev_open(struct sr_dev_inst *sdi)
        }
 
        ret = libusb_claim_interface(usb->devhdl, USB_INTERFACE);
-       if (ret < 0) {
+       if (ret != LIBUSB_SUCCESS) {
                sr_err("Failed to claim interface: %s.",
                        libusb_error_name(ret));
                sr_usb_close(usb);
                return SR_ERR;
        }
 
+       ret = drain_usb(usb, EP_REPLY);
+       if (ret != SR_OK)
+               return ret;
+
        sdi->status = SR_ST_ACTIVE;
 
        devc->active_fpga_config = FPGA_NOCONF;