Add ioctls USBTMC_IOCTL_GET_TIMEOUT / USBTMC_IOCTL_SET_TIMEOUT to
get/set I/O timeout for specific file handle.

Different operations on an instrument can take different lengths of
time thus it is important to be able to set the timeout slightly
longer than the expected duration of each operation to optimise the
responsiveness of the application. As the instrument may be shared by
multiple applications the timeout should be settable on a per file
descriptor basis.

Tested-by: Dave Penkler <dpenk...@gmail.com>
Reviewed-by: Steve Bayless <steve_bayl...@keysight.com>
Signed-off-by: Dave Penkler <dpenk...@gmail.com>
Signed-off-by: Guido Kiener <guido.kie...@rohde-schwarz.com>
---
 drivers/usb/class/usbtmc.c   | 58 +++++++++++++++++++++++++++++++++---
 include/uapi/linux/usb/tmc.h |  2 ++
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 5754354429d8..ad7872003420 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -30,6 +30,8 @@
  */
 #define USBTMC_SIZE_IOBUFFER   2048
 
+/* Minimum USB timeout (in milliseconds) */
+#define USBTMC_MIN_TIMEOUT     100
 /* Default USB timeout (in milliseconds) */
 #define USBTMC_TIMEOUT         5000
 
@@ -116,6 +118,7 @@ struct usbtmc_file_data {
        struct usbtmc_device_data *data;
        struct list_head file_elem;
 
+       u32            timeout;
        u8             srq_byte;
        atomic_t       srq_asserted;
 
@@ -163,6 +166,7 @@ static int usbtmc_open(struct inode *inode, struct file 
*filp)
        file_data->data = data;
 
        /* copy default values from device settings */
+       file_data->timeout = USBTMC_TIMEOUT;
        file_data->TermChar = data->TermChar;
        file_data->TermCharEnabled = data->TermCharEnabled;
        file_data->auto_abort = data->auto_abort;
@@ -478,7 +482,7 @@ static int usbtmc488_ioctl_read_stb(struct usbtmc_file_data 
*file_data,
                rv = wait_event_interruptible_timeout(
                        data->waitq,
                        atomic_read(&data->iin_data_valid) != 0,
-                       USBTMC_TIMEOUT);
+                       file_data->timeout);
                if (rv < 0) {
                        dev_dbg(dev, "wait interrupted %d\n", rv);
                        goto exit;
@@ -613,7 +617,8 @@ static int send_request_dev_dep_msg_in(struct 
usbtmc_file_data *file_data,
        retval = usb_bulk_msg(data->usb_dev,
                              usb_sndbulkpipe(data->usb_dev,
                                              data->bulk_out),
-                             buffer, USBTMC_HEADER_SIZE, &actual, 
USBTMC_TIMEOUT);
+                             buffer, USBTMC_HEADER_SIZE,
+                             &actual, file_data->timeout);
 
        /* Store bTag (in case we need to abort) */
        data->bTag_last_write = data->bTag;
@@ -681,7 +686,7 @@ static ssize_t usbtmc_read(struct file *filp, char __user 
*buf,
                                      usb_rcvbulkpipe(data->usb_dev,
                                                      data->bulk_in),
                                      buffer, USBTMC_SIZE_IOBUFFER, &actual,
-                                     USBTMC_TIMEOUT);
+                                     file_data->timeout);
 
                dev_dbg(dev, "usb_bulk_msg: retval(%u), done(%zu), 
remaining(%zu), actual(%d)\n", retval, done, remaining, actual);
 
@@ -854,7 +859,7 @@ static ssize_t usbtmc_write(struct file *filp, const char 
__user *buf,
                                              usb_sndbulkpipe(data->usb_dev,
                                                              data->bulk_out),
                                              buffer, n_bytes,
-                                             &actual, USBTMC_TIMEOUT);
+                                             &actual, file_data->timeout);
                        if (retval != 0)
                                break;
                        n_bytes -= actual;
@@ -1211,6 +1216,41 @@ static int usbtmc_ioctl_indicator_pulse(struct 
usbtmc_device_data *data)
        return rv;
 }
 
+/*
+ * Get the usb timeout value
+ */
+static int usbtmc_ioctl_get_timeout(struct usbtmc_file_data *file_data,
+                               void __user *arg)
+{
+       __u32 timeout;
+
+       timeout = file_data->timeout;
+
+       return put_user(timeout, (__u32 __user *)arg);
+}
+
+/*
+ * Set the usb timeout value
+ */
+static int usbtmc_ioctl_set_timeout(struct usbtmc_file_data *file_data,
+                               void __user *arg)
+{
+       __u32 timeout;
+
+       if (get_user(timeout, (__u32 __user *)arg))
+               return -EFAULT;
+
+       /* Note that timeout = 0 means
+        * MAX_SCHEDULE_TIMEOUT in usb_control_msg
+        */
+       if (timeout < USBTMC_MIN_TIMEOUT)
+               return -EINVAL;
+
+       file_data->timeout = timeout;
+
+       return 0;
+}
+
 static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long 
arg)
 {
        struct usbtmc_file_data *file_data;
@@ -1251,6 +1291,16 @@ static long usbtmc_ioctl(struct file *file, unsigned int 
cmd, unsigned long arg)
                retval = usbtmc_ioctl_abort_bulk_in(data);
                break;
 
+       case USBTMC_IOCTL_GET_TIMEOUT:
+               retval = usbtmc_ioctl_get_timeout(file_data,
+                                                 (void __user *)arg);
+               break;
+
+       case USBTMC_IOCTL_SET_TIMEOUT:
+               retval = usbtmc_ioctl_set_timeout(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 03f6adc8f35b..d6de192150f4 100644
--- a/include/uapi/linux/usb/tmc.h
+++ b/include/uapi/linux/usb/tmc.h
@@ -46,6 +46,8 @@
 #define USBTMC_IOCTL_ABORT_BULK_IN     _IO(USBTMC_IOC_NR, 4)
 #define USBTMC_IOCTL_CLEAR_OUT_HALT    _IO(USBTMC_IOC_NR, 6)
 #define USBTMC_IOCTL_CLEAR_IN_HALT     _IO(USBTMC_IOC_NR, 7)
+#define USBTMC_IOCTL_GET_TIMEOUT       _IOR(USBTMC_IOC_NR, 9, unsigned int)
+#define USBTMC_IOCTL_SET_TIMEOUT       _IOW(USBTMC_IOC_NR, 10, unsigned int)
 #define USBTMC488_IOCTL_GET_CAPS       _IOR(USBTMC_IOC_NR, 17, unsigned char)
 #define USBTMC488_IOCTL_READ_STB       _IOR(USBTMC_IOC_NR, 18, unsigned char)
 #define USBTMC488_IOCTL_REN_CONTROL    _IOW(USBTMC_IOC_NR, 19, unsigned char)
-- 
2.17.0

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