USB: usbtmc: Change magic number to constant

These patches implement a modification of the USBTMC
protocol to allow operation with Rigol equipment. Cosmetic change to show
that 12 is the USBTMC header size.

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

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 8ebd06b..609dbc2 100644 (file)
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -640,8 +640,8 @@ static ssize_t usbtmc_write(struct file *filp, const char __user *buf,
        done = 0;
 
        while (remaining > 0) {
-               if (remaining > USBTMC_SIZE_IOBUFFER - 12) {
-                       this_part = USBTMC_SIZE_IOBUFFER - 12;
+               if (remaining > USBTMC_SIZE_IOBUFFER - USBTMC_HEADER_SIZE) {
+                       this_part = USBTMC_SIZE_IOBUFFER - USBTMC_HEADER_SIZE;
                        buffer[8] = 0;
                } else {
                        this_part = remaining;
@@ -662,13 +662,13 @@ static ssize_t usbtmc_write(struct file *filp, const char __user *buf,
                buffer[10] = 0; /* Reserved */
                buffer[11] = 0; /* Reserved */
 
-               if (copy_from_user(&buffer[12], buf + done, this_part)) {
+               if (copy_from_user(&buffer[USBTMC_HEADER_SIZE], buf + done, this_part)) {
                        retval = -EFAULT;
                        goto exit;
                }
 
-               n_bytes = roundup(12 + this_part, 4);
-               memset(buffer + 12 + this_part, 0, n_bytes - (12 + this_part));
+               n_bytes = roundup(USBTMC_HEADER_SIZE + this_part, 4);
+               memset(buffer + USBTMC_HEADER_SIZE + this_part, 0, n_bytes - (USBTMC_HEADER_SIZE + this_part));
 
                do {
                        retval = usb_bulk_msg(data->usb_dev,