Re: [PATCH] usb: add sysfs configuration interface for CP2101

[Dirk Eibach <eibach@gdsys.de>]

From: Dirk Eibach <eibach@gdsys.de>

The usb configuration data for the Silabs CP2101 usb to uart bridge 
controller can be customized:
- Vendor ID
- Product ID
- Power Descriptor
- Release Number
- Serial Number
- Product Description String

Silabs provides a windows-only tool to do that.
Since we use linux-only machines in our production-environment, we have no 
proper way to customize the chips for our purpose.
So I added sysfs configuration support to the linux driver.

Signed-off-by: Dirk Eibach <eibach@gdsys.de>
---
diff -purN linux-2.6.24/Documentation/ABI/testing/sysfs-bus-usb-devices-cp2101 linux-2.6.24-diff/Documentation/ABI/testing/sysfs-bus-usb-devices-cp2101
--- linux-2.6.24/Documentation/ABI/testing/sysfs-bus-usb-devices-cp2101	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.24-diff/Documentation/ABI/testing/sysfs-bus-usb-devices-cp2101	2008-03-03 09:29:21.883042194 +0100
@@ -0,0 +1,44 @@
+What:		cp2101 sysfs device customization-interface
+Date:		03.03.2008
+KernelVersion:	2.6.26
+Contact:	Dirk Eibach <eibach@gdsys.de>
+Description:	
+
+The usb configuration data for the Silabs CP2101 usb to uart bridge 
+controller are stored in an on-chip eeprom and can be customized:
+- Vendor ID
+- Product ID
+- Power Descriptor
+- Release Number
+- Serial Number
+- Product Description String
+
+When loaded with module parameter "enable_config=1" the cp2101 driver offers 
+the following sysfs attributes to customize USB configuration data:
+
+reload
+	write "1" to reboot CP210x and activate the new configuration
+
+vendor_id
+	write 16 bit value to set
+
+product_id
+	write 16 bit value to set
+
+productstring
+	write up to 126 characters to set
+
+serialnumber
+	write up to 63 characters to set
+
+self_powered
+	write "1" to set, "0" to unset
+
+max_power
+	write 8 bit value (unit 2 mA) to set
+
+release_version
+	write 16 bit BCD-value to set (0x1234 => version 12.34)
+
+lock_forever
+	write "1" to lock the settings permanently (*no way back*)
diff -purN linux-2.6.24/drivers/usb/serial/cp2101.c linux-2.6.24-diff/drivers/usb/serial/cp2101.c
--- linux-2.6.24/drivers/usb/serial/cp2101.c	2008-01-24 23:58:37.000000000 +0100
+++ linux-2.6.24-diff/drivers/usb/serial/cp2101.c	2008-03-03 10:24:16.905807660 +0100
@@ -18,6 +18,8 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/platform_device.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/tty.h>
@@ -52,6 +54,8 @@ static void cp2101_shutdown(struct usb_s
 
 static int debug;
 
+static int enable_config;
+
 static struct usb_device_id id_table [] = {
 	{ USB_DEVICE(0x08e6, 0x5501) }, /* Gemalto Prox-PU/CU contactless smartcard reader */
 	{ USB_DEVICE(0x0FCF, 0x1003) }, /* Dynastream ANT development board */
@@ -125,6 +129,7 @@ static struct usb_serial_driver cp2101_d
 #define CP2101_CONTROL		0x07	/* Flow control line states */
 #define CP2101_MODEMCTL		0x13	/* Modem controls */
 #define CP2101_CONFIG_6		0x19	/* 6 bytes of config data ??? */
+#define CP2101_EEPROM		0xFF	/* write configuration eeprom */
 
 /* CP2101_UART */
 #define UART_ENABLE		0x0001
@@ -167,6 +172,20 @@ static struct usb_serial_driver cp2101_d
 #define CONTROL_WRITE_DTR	0x0100
 #define CONTROL_WRITE_RTS	0x0200
 
+/* CP2101 CONFIGURATION EEPROM */
+#define EEPROM_RELOAD		0x0008
+#define EEPROM_VENDOR_ID	0x3701
+#define EEPROM_PRODUCT_ID	0x3702
+#define EEPROM_PRODUCTSTRING	0x3703
+#define EEPROM_SERIALNUMBER	0x3704
+#define EEPROM_POWER_ATTRIB	0x3705
+#define EEPROM_MAX_POWER	0x3706
+#define EEPROM_RELEASE_VERSION	0x3707
+#define EEPROM_LOCK		0x370a
+
+#define SERIALNUMBER_MAX_CHARS	63
+#define PRODUCTSTRING_MAX_CHARS	126
+
 /*
  * cp2101_get_config
  * Reads from the CP2101 configuration registers
@@ -704,11 +723,309 @@ static void cp2101_break_ctl (struct usb
 	cp2101_set_config(port, CP2101_BREAK, &state, 2);
 }
 
+/*
+ * When loaded with module parameter "enable_config=1" the driver offers
+ * sysfs attributes to customize USB configuration data as described in
+ * Documentation/ABI/testing/sysfs-bus-usb-devices-cp2101.
+ */
+
+static ssize_t write_reload(struct device *dev, struct device_attribute *attr,
+	const char *buf, size_t count)
+{
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long reload;
+
+	if (strict_strtoul(buf, 0, &reload))
+		return -EINVAL;
+
+	/* writing "0" does not trigger */
+	if (!reload)
+		return count;
+
+	usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_RELOAD,
+		0, NULL, 0, 300);
+
+	/* this request is expected to fail because cp210x reboots */
+
+	return count;
+}
+
+static DEVICE_ATTR(reload, S_IWUGO, NULL, write_reload);
+
+static ssize_t write_vendor_id(struct device *dev,
+	struct device_attribute *attr,	const char *buf, size_t count)
+{
+	int result;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long vendor_id;
+
+	if (strict_strtoul(buf, 0, &vendor_id))
+		return -EINVAL;
+
+	if (!vendor_id || vendor_id > 0xffff)
+		return -EINVAL;
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_VENDOR_ID,
+		vendor_id, NULL, 0, 300);
+
+	if (result)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(vendor_id, S_IWUGO, NULL, write_vendor_id);
+
+static ssize_t write_product_id(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int result;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long product_id;
+
+	if (strict_strtoul(buf, 0, &product_id))
+		return -EINVAL;
+
+	if (!product_id || product_id > 0xffff)
+		return -EINVAL;
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_PRODUCT_ID,
+		product_id, NULL, 0, 300);
+
+	if (result)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(product_id, S_IWUGO, NULL, write_product_id);
+
+static ssize_t write_serialnumber(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int result;
+	unsigned int k;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+	u8 serial_stringsize = 2 + 2*count;
+	char *serial;
+
+	if (count > SERIALNUMBER_MAX_CHARS)
+		return -EINVAL;
+
+	serial = kmalloc(serial_stringsize, GFP_KERNEL);
+	if (!serial)
+		return -ENOMEM;
+
+	serial[0] = serial_stringsize;
+	serial[1] = USB_DT_STRING;
+
+	/* convert to utf-16 */
+	for (k = 0; k < count; ++k) {
+		serial[2+2*k] = buf[k];
+		serial[2+2*k+1] = 0;
+	}
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_SERIALNUMBER,
+		0, serial, serial_stringsize, 300);
+
+	kfree(serial);
+
+	if (result != serial_stringsize)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(serialnumber, S_IWUGO, NULL, write_serialnumber);
+
+
+static ssize_t write_productstring(struct device *dev,
+	struct device_attribute *attr,	const char *buf, size_t count)
+{
+	int result;
+	unsigned int k;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+	u8 product_stringsize = 2 + 2*count;
+	char *product;
+
+	if (count > PRODUCTSTRING_MAX_CHARS)
+		return -EINVAL;
+
+	product = kmalloc(product_stringsize, GFP_KERNEL);
+	if (!product)
+		return -ENOMEM;
+
+	product[0] = product_stringsize;
+	product[1] = USB_DT_STRING;
+
+	/* convert to utf-16 */
+	for (k = 0; k < count; ++k) {
+		product[2+2*k] = buf[k];
+		product[2+2*k+1] = 0;
+	}
+
+	result = usb_control_msg(usbdev,
+			usb_sndctrlpipe(usbdev, 0),
+			CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE,
+			EEPROM_PRODUCTSTRING, 0,
+			product, product_stringsize, 300);
+
+	kfree(product);
+
+	if (result != product_stringsize)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(productstring, S_IWUGO, NULL, write_productstring);
+
+static ssize_t write_self_powered(struct device *dev,
+	struct device_attribute *attr,	const char *buf, size_t count)
+{
+	int result;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long self_powered;
+
+	if (strict_strtoul(buf, 0, &self_powered))
+		return -EINVAL;
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_POWER_ATTRIB,
+		self_powered ? 0x00c0 : 0x0080, NULL, 0, 300);
+
+	if (result)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(self_powered, S_IWUGO, NULL, write_self_powered);
+
+static ssize_t write_max_power(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int result;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long max_power;
+
+	if (strict_strtoul(buf, 0, &max_power))
+		return -EINVAL;
+
+	if (!max_power || max_power > 0xff)
+		return -EINVAL;
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_MAX_POWER,
+		max_power, NULL, 0, 300);
+
+	if (result)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(max_power, S_IWUGO, NULL, write_max_power);
+
+static ssize_t write_release_version(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	int result;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long release_version;
+
+	if (strict_strtoul(buf, 0, &release_version))
+		return -EINVAL;
+
+	if (release_version > 0xffff)
+		return -EINVAL;
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_RELEASE_VERSION,
+		release_version, NULL, 0, 300);
+
+	if (result)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(release_version, S_IWUGO, NULL, write_release_version);
+
+static ssize_t write_lock_forever(struct device *dev,
+	struct device_attribute *attr,	const char *buf, size_t count)
+{
+	int result;
+	struct usb_device *usbdev = container_of(dev, struct usb_device, dev);
+
+	unsigned long lock;
+
+	if (strict_strtoul(buf, 0, &lock))
+		return -EINVAL;
+
+	if (lock != 1)
+		return count;
+
+	result = usb_control_msg(usbdev,
+		usb_sndctrlpipe(usbdev, 0),
+		CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_LOCK,
+		0x00f0, NULL, 0, 300);
+
+	if (result)
+		return result;
+
+	return count;
+}
+
+static DEVICE_ATTR(lock_forever, S_IWUGO, NULL, write_lock_forever);
+
+static struct attribute *cp2101_attributes[] = {
+	&dev_attr_reload.attr,
+	&dev_attr_vendor_id.attr,
+	&dev_attr_product_id.attr,
+	&dev_attr_productstring.attr,
+	&dev_attr_serialnumber.attr,
+	&dev_attr_self_powered.attr,
+	&dev_attr_max_power.attr,
+	&dev_attr_release_version.attr,
+	&dev_attr_lock_forever.attr,
+	NULL
+};
+
+static const struct attribute_group cp2101_group = {
+	.attrs = cp2101_attributes,
+};
+
 static int cp2101_startup (struct usb_serial *serial)
 {
+	int err;
+
 	/* CP2101 buffers behave strangely unless device is reset */
 	usb_reset_device(serial->dev);
-	return 0;
+
+	if (!enable_config)
+		return 0;
+
+	err = sysfs_create_group(&serial->dev->dev.kobj, &cp2101_group);
+
+	return err;
 }
 
 static void cp2101_shutdown (struct usb_serial *serial)
@@ -721,6 +1038,11 @@ static void cp2101_shutdown (struct usb_
 	for (i=0; i < serial->num_ports; ++i) {
 		cp2101_cleanup(serial->port[i]);
 	}
+
+	if (!enable_config)
+		return;
+
+	sysfs_remove_group(&serial->dev->dev.kobj, &cp2101_group);
 }
 
 static int __init cp2101_init (void)
@@ -758,3 +1080,6 @@ MODULE_LICENSE("GPL");
 
 module_param(debug, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(debug, "Enable verbose debugging messages");
+
+module_param(enable_config, bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(enable_config, "Enable sysfs access to configuration eeprom.");