[PATCH v3 4/5] Add ioctl to retrieve USBTMC-USB488 capabilities

[Dave Penkler <dpenkler@gmail.com>]

This is a convenience function to obtain an instrument's capabilities
from its file descriptor without having to access sysfs from the user
program.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
---
 drivers/usb/class/usbtmc.c   | 12 ++++++++++++
 include/uapi/linux/usb/tmc.h | 21 ++++++++++++++++++---
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index bb9a6ab..deca4b5 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -103,6 +103,9 @@ struct usbtmc_device_data {
 	u16            iin_wMaxPacketSize;
 	atomic_t       srq_asserted;
 
+	/* coalesced usb488_caps from usbtmc_dev_capabilities */
+	u8 usb488_caps;
+
 	u8 rigol_quirk;
 
 	/* attributes from the USB TMC spec for this device */
@@ -1001,6 +1004,7 @@ static int get_capabilities(struct usbtmc_device_data *data)
 	data->capabilities.device_capabilities = buffer[5];
 	data->capabilities.usb488_interface_capabilities = buffer[14];
 	data->capabilities.usb488_device_capabilities = buffer[15];
+	data->usb488_caps = (buffer[14] & 0x07) | ((buffer[15] & 0x0f) << 4);
 	rv = 0;
 
 err_out:
@@ -1176,6 +1180,14 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		retval = usbtmc_ioctl_abort_bulk_in(data);
 		break;
 
+	case USBTMC488_IOCTL_GET_CAPS:
+		retval = copy_to_user((void __user *)arg,
+				&data->usb488_caps,
+				sizeof(data->usb488_caps));
+		if (retval)
+			retval = -EFAULT;
+		break;
+
 	case USBTMC488_IOCTL_READ_STB:
 		retval = usbtmc488_ioctl_read_stb(data, arg);
 		break;
diff --git a/include/uapi/linux/usb/tmc.h b/include/uapi/linux/usb/tmc.h
index 49060ea..2606664 100644
--- a/include/uapi/linux/usb/tmc.h
+++ b/include/uapi/linux/usb/tmc.h
@@ -2,12 +2,14 @@
  * Copyright (C) 2007 Stefan Kopp, Gechingen, Germany
  * Copyright (C) 2008 Novell, Inc.
  * Copyright (C) 2008 Greg Kroah-Hartman <gregkh@suse.de>
+ * Copyright (C) 2015 Dave Penkler <dpenkler@gmail.com>
  *
  * This file holds USB constants defined by the USB Device Class
- * Definition for Test and Measurement devices published by the USB-IF.
+ * and USB488 Subclass Definitions for Test and Measurement devices
+ * published by the USB-IF.
  *
- * It also has the ioctl definitions for the usbtmc kernel driver that
- * userspace needs to know about.
+ * It also has the ioctl and capability definitions for the
+ * usbtmc kernel driver that userspace needs to know about.
  */
 
 #ifndef __LINUX_USB_TMC_H
@@ -40,6 +42,19 @@
 #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 USBTMC488_IOCTL_GET_CAPS	_IO(USBTMC_IOC_NR, 17)
 #define USBTMC488_IOCTL_READ_STB	_IOR(USBTMC_IOC_NR, 18, unsigned char)
 
+/* Driver encoded usb488 capabilities */
+#define USBTMC488_CAPABILITY_TRIGGER         1
+#define USBTMC488_CAPABILITY_SIMPLE          2
+#define USBTMC488_CAPABILITY_REN_CONTROL     2
+#define USBTMC488_CAPABILITY_GOTO_LOCAL      2
+#define USBTMC488_CAPABILITY_LOCAL_LOCKOUT   2
+#define USBTMC488_CAPABILITY_488_DOT_2       4
+#define USBTMC488_CAPABILITY_DT1             16
+#define USBTMC488_CAPABILITY_RL1             32
+#define USBTMC488_CAPABILITY_SR1             64
+#define USBTMC488_CAPABILITY_FULL_SCPI       128
+
 #endif
-- 
2.5.1