USB: usbtmc: usbtmc_read sends multiple TMC header based on rigol_quirk

These patches implement a modification of the USBTMC
protocol to allow operation with Rigol equipment. The usbtmc_read function is
modified so if the quirk is active, the TMC header is sent with the size of
the data as the whole size of the request. If the quirk is inactive, the TMC
request is sent once per bulk transfer and with size limited to the bulk
transfer size. In the case of the quirk, only the first response contains the
TMC header and the others are just data.

Signed-off-by: Alexandre Peixoto Ferreira <alexandref75@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/usbtmc.c

@@ -455,21 +455,39 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf,
 		goto exit;
 	}
 
+	if (data->rigol_quirk) {
+		dev_dbg(dev, "usb_bulk_msg_in: count(%zu)\n", count);
+
+		retval = send_request_dev_dep_msg_in(data, count);
+
+		if (retval < 0) {
+			if (data->auto_abort)
+				usbtmc_ioctl_abort_bulk_out(data);
+			goto exit;
+		}
+	}
+
+	/* Loop until we have fetched everything we requested */
 	remaining = count;
+	this_part = remaining;
 	done = 0;
 
 	while (remaining > 0) {
-		if (remaining > USBTMC_SIZE_IOBUFFER - 12 - 3)
-			this_part = USBTMC_SIZE_IOBUFFER - 12 - 3;
-		else
-			this_part = remaining;
+		if (!(data->rigol_quirk)) {
+			dev_dbg(dev, "usb_bulk_msg_in: remaining(%zu), count(%zu)\n", remaining, count);
+
+			if (remaining > USBTMC_SIZE_IOBUFFER - USBTMC_HEADER_SIZE - 3)
+				this_part = USBTMC_SIZE_IOBUFFER - USBTMC_HEADER_SIZE - 3;
+			else
+				this_part = remaining;
 
 			retval = send_request_dev_dep_msg_in(data, this_part);
-		if (retval < 0) {
+			if (retval < 0) {
 			dev_err(dev, "usb_bulk_msg returned %d\n", retval);
-			if (data->auto_abort)
-				usbtmc_ioctl_abort_bulk_out(data);
-			goto exit;
+				if (data->auto_abort)
+					usbtmc_ioctl_abort_bulk_out(data);
+				goto exit;
+			}
 		}
 
 		/* Send bulk URB */
@@ -479,51 +497,109 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf,
 				      buffer, USBTMC_SIZE_IOBUFFER, &actual,
 				      USBTMC_TIMEOUT);
 
+		dev_dbg(dev, "usb_bulk_msg: retval(%u), done(%zu), remaining(%zu), actual(%d)\n", retval, done, remaining, actual);
+
 		/* Store bTag (in case we need to abort) */
 		data->bTag_last_read = data->bTag;
 
 		if (retval < 0) {
-			dev_err(dev, "Unable to read data, error %d\n", retval);
+			dev_dbg(dev, "Unable to read data, error %d\n", retval);
 			if (data->auto_abort)
 				usbtmc_ioctl_abort_bulk_in(data);
 			goto exit;
 		}
 
-		/* How many characters did the instrument send? */
-		n_characters = buffer[4] +
-			       (buffer[5] << 8) +
-			       (buffer[6] << 16) +
-			       (buffer[7] << 24);
+		/* Parse header in first packet */
+		if ((done == 0) || (!(data->rigol_quirk))) {
+			/* Sanity checks for the header */
+			if (actual < USBTMC_HEADER_SIZE) {
+				dev_err(dev, "Device sent too small first packet: %u < %u\n", actual, USBTMC_HEADER_SIZE);
+				if (data->auto_abort)
+					usbtmc_ioctl_abort_bulk_in(data);
+				goto exit;
+			}
 
-		/* Ensure the instrument doesn't lie about it */
-		if(n_characters > actual - 12) {
-			dev_err(dev, "Device lies about message size: %u > %d\n", n_characters, actual - 12);
-			n_characters = actual - 12;
-		}
+			if (buffer[0] != 2) {
+				dev_err(dev, "Device sent reply with wrong MsgID: %u != 2\n", buffer[0]);
+				if (data->auto_abort)
+					usbtmc_ioctl_abort_bulk_in(data);
+				goto exit;
+			}
 
-		/* Ensure the instrument doesn't send more back than requested */
-		if(n_characters > this_part) {
-			dev_err(dev, "Device returns more than requested: %zu > %zu\n", done + n_characters, done + this_part);
-			n_characters = this_part;
-		}
+			if (buffer[1] != data->bTag_last_write) {
+				dev_err(dev, "Device sent reply with wrong bTag: %u != %u\n", buffer[1], data->bTag_last_write);
+				if (data->auto_abort)
+					usbtmc_ioctl_abort_bulk_in(data);
+				goto exit;
+			}
 
-		/* Bound amount of data received by amount of data requested */
-		if (n_characters > this_part)
-			n_characters = this_part;
+			/* How many characters did the instrument send? */
+			n_characters = buffer[4] +
+				       (buffer[5] << 8) +
+				       (buffer[6] << 16) +
+				       (buffer[7] << 24);
 
-		/* Copy buffer to user space */
-		if (copy_to_user(buf + done, &buffer[12], n_characters)) {
-			/* There must have been an addressing problem */
-			retval = -EFAULT;
-			goto exit;
+			if (n_characters > this_part) {
+				dev_err(dev, "Device wants to return more data than requested: %u > %zu\n", n_characters, count);
+				if (data->auto_abort)
+					usbtmc_ioctl_abort_bulk_in(data);
+				goto exit;
+			}
+
+			/* Remove the USBTMC header */
+			actual -= USBTMC_HEADER_SIZE;
+
+			/* Check if the message is smaller than requested */
+			if (data->rigol_quirk) {
+				if (remaining > n_characters)
+					remaining = n_characters;
+				/* Remove padding if it exists */
+				if (actual > remaining) 
+					actual = remaining;
+			}
+			else {
+				if (this_part > n_characters)
+					this_part = n_characters;
+				/* Remove padding if it exists */
+				if (actual > this_part) 
+					actual = this_part;
+			}
+
+			dev_dbg(dev, "Bulk-IN header: N_characters(%u), bTransAttr(%u)\n", n_characters, buffer[8]);
+
+			remaining -= actual;
+
+			/* Terminate if end-of-message bit received from device */
+			if ((buffer[8] &  0x01) && (actual >= n_characters))
+				remaining = 0;
+
+			dev_dbg(dev, "Bulk-IN header: remaining(%zu), buf(%p), buffer(%p) done(%zu)\n", remaining,buf,buffer,done);
+
+
+			/* Copy buffer to user space */
+			if (copy_to_user(buf + done, &buffer[USBTMC_HEADER_SIZE], actual)) {
+				/* There must have been an addressing problem */
+				retval = -EFAULT;
+				goto exit;
+			}
+			done += actual;
 		}
+		else  {
+			if (actual > remaining) 
+				actual = remaining;
 
-		done += n_characters;
-		/* Terminate if end-of-message bit received from device */
-		if ((buffer[8] &  0x01) && (actual >= n_characters + 12))
-			remaining = 0;
-		else
-			remaining -= n_characters;
+			remaining -= actual;
+
+			dev_dbg(dev, "Bulk-IN header cont: actual(%u), done(%zu), remaining(%zu), buf(%p), buffer(%p)\n", actual, done, remaining,buf,buffer);
+
+			/* Copy buffer to user space */
+			if (copy_to_user(buf + done, buffer, actual)) {
+				/* There must have been an addressing problem */
+				retval = -EFAULT;
+				goto exit;
+			}
+			done += actual;
+		}
 	}
 
 	/* Update file position value */