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

On Fri, 29 Feb 2008 13:31:11 +0100
Dirk Eibach <eibach@xxxxxxxx> wrote:

So here is a new try.


Please reissue the possibly-updated changelog and signed-off-by: with each
revision of a patch.

Please cc linux-usb on usb patches.

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 2008-02-29 13:15:58.168233146 +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 = false;

Should be either

static int enable_config;

or, if you're being very formal,

static bool enable_config = false;

or, if you're being less formal and want to avoid bloating the kernel image,

static bool enable_config;

+static ssize_t write_reload(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);
+
+ /* writing "0" does not trigger */
+ if (!strict_strtoul(buf, NULL, 0))
+ return count;
+
+ result = 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;
+}

The comment will suffice - there's no need to add the do-nothing `result'.

+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 = strict_strtoul(buf, NULL, 0);
+
+ 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 -EIO;
+
+ return count;
+}

usb_control_msg() already returns an errno - we should just propagate that
back to the caller rather than overwriting, say, -ENOMEM with -EIO.

+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 = strict_strtoul(buf, NULL, 0);
+
+ 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 -EIO;
+
+ return count;
+}

ditto

+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[2 + 2*SERIALNUMBER_MAX_CHARS];

128 bytes of stack is a little more than we'd like (the kernel is really
squeezy on stack space sometimes). kmalloc would be better...

+ if (count > SERIALNUMBER_MAX_CHARS)
+ return -EINVAL;
+
+ serial[0] = serial_stringsize;
+ serial[1] = USB_DT_STRING;
+
+ /* convert to utf-16 */
+ printk("#Max index: %d\n", serial_stringsize - 1);

checkpatch...

+ for (k = 0; k < count; ++k) {
+ printk("Address index %d and %d\n", 2+2*k, 2+2*k+1);
+ 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);
+
+ if (result != serial_stringsize)
+ return -EIO;
+
+ return count;
+}

...

+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 = strict_strtoul(buf, NULL, 0);
+
+ /* be really, really sure to know what you are doing here */
+ if (lock != 0xabadbabe)
+ return -EINVAL;

this is incomprehehsible without docs

+ result = usb_control_msg(usbdev,
+ usb_sndctrlpipe(usbdev, 0),
+ CP2101_EEPROM, REQTYPE_HOST_TO_DEVICE, EEPROM_LOCK,
+ 0x00f0, NULL, 0, 300);
+
+ if (result)
+ return -EIO;
+
+ 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 +1015,11 @@ 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 +1057,6 @@ 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.");


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