usb: usbtmc: Add ioctl for termination character

add USBTMC_IOCTL_CONFIG_TERMCHAR to control TermChar handling
for next read(). Controls field 'TermChar' and Bit 1 of field
'bmTransferAttributes' of REQUEST_DEV_DEP_MSG_IN BULK-OUT header.

Allows enabling/disabling of terminating a read on reception of
term_char individually for each read request.

Reviewed-by: Steve Bayless <steve_bayless@keysight.com>
Tested-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 40 insertions, 2 deletions

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index c77e0ac6260b..1b7b2e402adb 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -121,6 +121,8 @@ struct usbtmc_file_data {
         u8             srq_byte;
         atomic_t       srq_asserted;
         u8             eom_val;
+        u8             term_char;
+        bool           term_char_enabled;
 };
 
 /* Forward declarations */
@@ -157,7 +159,10 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
         mutex_lock(&data->io_mutex);
         file_data->data = data;
 
+        /* copy default values from device settings */
         file_data->timeout = USBTMC_TIMEOUT;
+        file_data->term_char = data->TermChar;
+        file_data->term_char_enabled = data->TermCharEnabled;
         file_data->eom_val = 1;
 
         INIT_LIST_HEAD(&file_data->file_elem);
@@ -634,9 +639,9 @@ static int send_request_dev_dep_msg_in(struct usbtmc_file_data *file_data,
         buffer[5] = transfer_size >> 8;
         buffer[6] = transfer_size >> 16;
         buffer[7] = transfer_size >> 24;
-        buffer[8] = data->TermCharEnabled * 2;
+        buffer[8] = file_data->term_char_enabled * 2;
         /* Use term character? */
-        buffer[9] = data->TermChar;
+        buffer[9] = file_data->term_char;
         buffer[10] = 0; /* Reserved */
         buffer[11] = 0; /* Reserved */
 
@@ -1298,6 +1303,28 @@ static int usbtmc_ioctl_eom_enable(struct usbtmc_file_data *file_data,
         return 0;
 }
 
+/*
+ * Configure termination character for read()
+ */
+static int usbtmc_ioctl_config_termc(struct usbtmc_file_data *file_data,
+                                void __user *arg)
+{
+        struct usbtmc_termchar termc;
+
+        if (copy_from_user(&termc, arg, sizeof(termc)))
+                return -EFAULT;
+
+        if ((termc.term_char_enabled > 1) ||
+                (termc.term_char_enabled &&
+                !(file_data->data->capabilities.device_capabilities & 1)))
+                return -EINVAL;
+
+        file_data->term_char = termc.term_char;
+        file_data->term_char_enabled = termc.term_char_enabled;
+
+        return 0;
+}
+
 static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
         struct usbtmc_file_data *file_data;
@@ -1353,6 +1380,11 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
                                                  (void __user *)arg);
                 break;
 
+        case USBTMC_IOCTL_CONFIG_TERMCHAR:
+                retval = usbtmc_ioctl_config_termc(file_data,
+                                                   (void __user *)arg);
+                break;
+
         case USBTMC488_IOCTL_GET_CAPS:
                 retval = copy_to_user((void __user *)arg,
                                 &data->usb488_caps,
diff --git a/include/uapi/linux/usb/tmc.h b/include/uapi/linux/usb/tmc.h
index e7317dfdd2ae..729af2f861a4 100644
--- a/include/uapi/linux/usb/tmc.h
+++ b/include/uapi/linux/usb/tmc.h
@@ -40,6 +40,11 @@
 #define USBTMC488_REQUEST_GOTO_LOCAL                    161
 #define USBTMC488_REQUEST_LOCAL_LOCKOUT                 162
 
+struct usbtmc_termchar {
+        __u8 term_char;
+        __u8 term_char_enabled;
+} __attribute__ ((packed));
+
 /* Request values for USBTMC driver's ioctl entry point */
 #define USBTMC_IOC_NR                   91
 #define USBTMC_IOCTL_INDICATOR_PULSE    _IO(USBTMC_IOC_NR, 1)
@@ -51,6 +56,7 @@
 #define USBTMC_IOCTL_GET_TIMEOUT        _IOR(USBTMC_IOC_NR, 9, __u32)
 #define USBTMC_IOCTL_SET_TIMEOUT        _IOW(USBTMC_IOC_NR, 10, __u32)
 #define USBTMC_IOCTL_EOM_ENABLE         _IOW(USBTMC_IOC_NR, 11, __u8)
+#define USBTMC_IOCTL_CONFIG_TERMCHAR    _IOW(USBTMC_IOC_NR, 12, struct usbtmc_termchar)
 
 #define USBTMC488_IOCTL_GET_CAPS        _IOR(USBTMC_IOC_NR, 17, unsigned char)
 #define USBTMC488_IOCTL_READ_STB        _IOR(USBTMC_IOC_NR, 18, unsigned char)