Driver exposes a character device /dev/pico_rng. Updated driver to support the character device. Tested with dd and cat. I am getting better performance than with Python, no shocker there.

driver/pico_rng.c

@@ -11,6 +11,7 @@
 #include <linux/semaphore.h>
 #include <asm/uaccess.h>
 
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Mickey Malone");
 MODULE_DESCRIPTION("Random number generator using a Raspberry Pi Pico");
@@ -21,7 +22,6 @@ MODULE_VERSION("1.0");
  **/
 #define VENDOR_ID             0x0
 #define PRODUCT_ID            0x4
-#define SC_MINOR_BASE         31
 
 /**
  * Helper macros
@@ -35,6 +35,21 @@ static int debug = 0;
 module_param(debug, int, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
 MODULE_PARM_DESC(debug, "Set the log level to debug");
 
+static int timeout = 500;
+module_param(timeout, int, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+MODULE_PARM_DESC(timeout, "Set the read timeout for the pico rng usb device");
+
+/**
+ * The main data structure for this module
+ **/
+struct pico_rng_data {
+	struct usb_device                      *dev;
+	struct usb_interface                   *interface;
+	struct usb_endpoint_descriptor         *endpoint;
+	char                                   *buffer;
+	int                                    pipe;
+} module_data;
+
 /**
  * Prototype Functions
  **/
@@ -43,13 +58,8 @@ static void pico_rng_usb_disconnect(struct usb_interface *interface);
 static int __init pico_rng_driver_init(void);
 static void __exit pico_rng_driver_exit(void);
 
-/**
+static ssize_t pico_rng_read(struct file *file, char __user *user_buffer, size_t size, loff_t *offset);
 static int pico_rng_open(struct inode *inode, struct file *file);
-static int pico_rng_release(struct inode *inode, struct file *file);
-static ssize_t pico_rng_write(struct file *file, const char __user *user_buf, size_t count, loff_t *ppos);
-static ssize_t pico_rng_read(struct file *file, char __user *user, size_t count, loff_t *ppos);
-**/
-
 
 /**
  * Data structure of the USB vid:pid device that we will support
@@ -73,13 +83,63 @@ static struct usb_driver pico_rng_usb_driver = {
  * File operations data structure for the character device
  * that will be implemented in this module
  **/
-/**static struct file_operations pico_rng_fops = {
+static struct file_operations pico_rng_fops = {
 	.owner          = THIS_MODULE,
-	.open           = pico_rng_open,
 	.read           = pico_rng_read,
-	.release        = pico_rng_release,
+	.open           = pico_rng_open,
 };
-**/
+
+/**
+ * USB class data structure
+ **/
+ struct usb_class_driver pico_rng_usb_class = {
+	.name           = "pico_rng",
+	.fops           = &pico_rng_fops,
+};
+
+/**
+ * File ops:open
+ **/
+static int pico_rng_open(struct inode *inode, struct file *file)
+{
+	LOGGER_DEBUG("inside pico_rng_open with inode %p file %p\n", inode, file);
+	return 0;
+}
+
+/**
+ * File ops:read
+ **/
+static ssize_t pico_rng_read(struct file *file, char __user *user_buffer, size_t size, loff_t *offset)
+{
+	int actual_length = 0;
+	int retval = 0;
+
+	LOGGER_DEBUG("inside pico_rng_read with file %p, user_buffer %p, size %ld, offset %lld\n", file, user_buffer, size, *offset);
+
+    // int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe, void *data, int len, int *actual_length, int timeout)
+	LOGGER_DEBUG("Calling usb_bulk_msg dev %p, pipe %d, buffer %p, size %d, and timeout %d", \
+	        module_data.dev, module_data.pipe, module_data.buffer, module_data.endpoint->wMaxPacketSize, timeout);
+
+    retval = usb_bulk_msg(module_data.dev, 
+	                      module_data.pipe,
+						  module_data.buffer,
+						  module_data.endpoint->wMaxPacketSize,
+						  &actual_length,
+						  timeout);
+
+    if(retval)
+	{
+		return -EFAULT;
+	}
+
+    LOGGER_DEBUG("Copying %d bytest of random data to userspace with offset %lld\n", actual_length, *offset);
+	if(copy_to_user(user_buffer, module_data.buffer, module_data.endpoint->wMaxPacketSize))
+	{
+        return -EFAULT;
+	}
+
+    return module_data.endpoint->wMaxPacketSize;
+}
 
 /**
  * USB: Probe
@@ -87,45 +147,50 @@ static struct usb_driver pico_rng_usb_driver = {
  **/
 static int pico_rng_usb_probe(struct usb_interface *interface, const struct usb_device_id *id)
 {
-	struct usb_device              *dev = interface_to_usbdev(interface);
-	struct usb_endpoint_descriptor *endpoint = NULL;
 	int retval = -ENODEV;
-	char                           *buffer;
-	int                            actual_length;
-	int                            pipe = 0;
 
-	retval = usb_find_bulk_in_endpoint(interface->cur_altsetting, &endpoint);
+    module_data.dev = interface_to_usbdev(interface);
+	if(!module_data.dev)
+	{
+		LOGGER_ERR("Unable to locate usb device");
+		return retval;
+	}
+
+	module_data.interface = interface;
+	if(!module_data.interface)
+	{
+		LOGGER_ERR("Invalid interface");
+		return retval;
+	}
+
+	retval = usb_find_bulk_in_endpoint(module_data.interface->cur_altsetting, &(module_data.endpoint));
 	if(retval)
 	{
         LOGGER_ERR("Unable to find bulk endpoint %d\n", retval);
 		return(retval);
     }
 
-	pipe = usb_rcvbulkpipe(dev, endpoint->bEndpointAddress);
+	module_data.pipe = usb_rcvbulkpipe(module_data.dev, module_data.endpoint->bEndpointAddress);
 
-	LOGGER_DEBUG("endpoint found %p with pipe %d", endpoint, pipe);
+	LOGGER_DEBUG("endpoint found %p with pipe %d", module_data.endpoint, module_data.pipe);
 
-	buffer = kmalloc(endpoint->wMaxPacketSize, GFP_KERNEL);
+    module_data.buffer = NULL;
+	module_data.buffer = kmalloc(module_data.endpoint->wMaxPacketSize, GFP_KERNEL);
+	if(!module_data.buffer)
+	{
+        LOGGER_ERR("failed to allocate buffer");
+		return -1;
+	}
+
+	retval = usb_register_dev(module_data.interface, &pico_rng_usb_class);
+	if(retval)
+	{
+		LOGGER_ERR("not able to get a minor for this device\n");
+		return -1;
+	}
 
     // int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe, void *data, int len, int *actual_length, int timeout)
-    retval = usb_bulk_msg (dev,
+    //retval = usb_bulk_msg(dev, pipe, buffer, 64, &actual_length, 500);
-                           pipe,
-                           buffer,
-                           64,
-                           &actual_length,
-						   5000);
-
-    /* if the read was successful, copy the data to user space */
-    if (!retval)
-	{
-        LOGGER_INFO("%s\n", buffer);
-    }
-	else
-	{
-		LOGGER_INFO("usb_bulk_msg raised an error %d\n", retval);
-	}
-
-	kfree(buffer);
 
 	return retval;
 }
@@ -137,9 +202,14 @@ static int pico_rng_usb_probe(struct usb_interface *interface, const struct usb_
 static void pico_rng_usb_disconnect(struct usb_interface *interface)
 {
 	LOGGER_INFO("pico rng usb device disconnected\n");
+	usb_deregister_dev(module_data.interface, &pico_rng_usb_class);
+	module_data.dev = NULL;
+	module_data.interface = NULL;
+	module_data.pipe = 0;
+	kfree(module_data.buffer);
+	module_data.buffer = NULL;
 }
 
-
 static int __init pico_rng_driver_init(void)
 {
 	int retval = 0;
@@ -156,12 +226,18 @@ static int __init pico_rng_driver_init(void)
 		LOGGER_INFO("pico rng driver registered successfully\n");
 	}
 
-	return retval;
+	return 0;
 }
 
 static void __exit pico_rng_driver_exit(void)
 {
 	usb_deregister(&pico_rng_usb_driver);
+
+	if(module_data.buffer)
+	{
+		kfree(module_data.buffer);
+	}
+
 	return;
 }