Re: [PATCH v2] i2c-hid: introduce HID over i2c specification implementation

Hi JJ,

On Thu, Oct 18, 2012 at 11:07 AM, Jian-Jhong Ding [off-list ref] wrote:

Hi Benjamin,

Some suggestions to make the error messages more "human", and a little
question on the return value of i2c_hid_fetch_hid_descriptor.  Please see below:

I fully agree with the more "human" error messages.

However, for i2c_hid_fetch_hid_descriptor return values, I'm affraid I
can't use -EINVAL.

Jean Delvare (one of the i2c maintainers) told in his review of the v1:
"
These should all be -ENODEV in this function
[i2c_hid_fetch_hid_descriptor]: the device isn't what you
expected. EINVAL is for invalid argument.
"

So ENODEV is the right return value.

Anyway, thanks for the review.

Cheers,
Benjamin

Benjamin Tissoires [off-list ref] writes:

quoted

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
new file mode 100644
index 0000000..8b6c31a
--- /dev/null
+++ b/drivers/hid/i2c-hid/i2c-hid.c

@@ -0,0 +1,990 @@
+/*
+ * HID over I2C protocol implementation
+ *
+ * Copyright (c) 2012 Benjamin Tissoires <benjamin.tissoires-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
+ * Copyright (c) 2012 Ecole Nationale de l'Aviation Civile, France
+ *
+ * This code is partly based on "USB HID support for Linux":
+ *
+ *  Copyright (c) 1999 Andreas Gal
+ *  Copyright (c) 2000-2005 Vojtech Pavlik <vojtech-AlSwsSmVLrQ@public.gmane.org>
+ *  Copyright (c) 2005 Michael Haboustak <mike--vDbLwGUA7lNWk0Htik3J/w@public.gmane.org> for Concept2, Inc
+ *  Copyright (c) 2007-2008 Oliver Neukum
+ *  Copyright (c) 2006-2010 Jiri Kosina
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive for
+ * more details.
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/input.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/pm.h>
+#include <linux/device.h>
+#include <linux/wait.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/list.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/bug.h>
+#include <linux/hid.h>
+
+#include <linux/i2c/i2c-hid.h>
+
+/* flags */
+#define I2C_HID_STARTED              (1 << 0)
+#define I2C_HID_RESET_PENDING        (1 << 1)
+#define I2C_HID_READ_PENDING (1 << 2)
+
+#define I2C_HID_PWR_ON               0x00
+#define I2C_HID_PWR_SLEEP    0x01
+
+/* debug option */
+static bool debug = false;
+module_param(debug, bool, 0444);
+MODULE_PARM_DESC(debug, "print a lot of debug information");
+
+#define i2c_hid_dbg(ihid, fmt, arg...)       \
+     if (debug)                      \
+             dev_printk(KERN_DEBUG, &(ihid)->client->dev, fmt, ##arg)
+
+struct i2c_hid_desc {
+     __le16 wHIDDescLength;
+     __le16 bcdVersion;
+     __le16 wReportDescLength;
+     __le16 wReportDescRegister;
+     __le16 wInputRegister;
+     __le16 wMaxInputLength;
+     __le16 wOutputRegister;
+     __le16 wMaxOutputLength;
+     __le16 wCommandRegister;
+     __le16 wDataRegister;
+     __le16 wVendorID;
+     __le16 wProductID;
+     __le16 wVersionID;
+} __packed;
+
+struct i2c_hid_cmd {
+     unsigned int registerIndex;
+     __u8 opcode;
+     unsigned int length;
+     bool wait;
+};
+
+union command {
+     u8 data[0];
+     struct cmd {
+             __le16 reg;
+             __u8 reportTypeID;
+             __u8 opcode;
+     } __packed c;
+};
+
+#define I2C_HID_CMD(opcode_) \
+     .opcode = opcode_, .length = 4, \
+     .registerIndex = offsetof(struct i2c_hid_desc, wCommandRegister)
+
+/* fetch HID descriptor */
+static const struct i2c_hid_cmd hid_descr_cmd = { .length = 2 };
+/* fetch report descriptors */
+static const struct i2c_hid_cmd hid_report_descr_cmd = {
+             .registerIndex = offsetof(struct i2c_hid_desc,
+                     wReportDescRegister),
+             .opcode = 0x00,
+             .length = 2 };
+/* commands */
+static const struct i2c_hid_cmd hid_reset_cmd =              { I2C_HID_CMD(0x01),
+                                                       .wait = true };
+static const struct i2c_hid_cmd hid_get_report_cmd = { I2C_HID_CMD(0x02) };
+static const struct i2c_hid_cmd hid_set_report_cmd = { I2C_HID_CMD(0x03) };
+static const struct i2c_hid_cmd hid_get_idle_cmd =   { I2C_HID_CMD(0x04) };
+static const struct i2c_hid_cmd hid_set_idle_cmd =   { I2C_HID_CMD(0x05) };
+static const struct i2c_hid_cmd hid_get_protocol_cmd =       { I2C_HID_CMD(0x06) };
+static const struct i2c_hid_cmd hid_set_protocol_cmd =       { I2C_HID_CMD(0x07) };
+static const struct i2c_hid_cmd hid_set_power_cmd =  { I2C_HID_CMD(0x08) };
+/* read/write data register */
+static const struct i2c_hid_cmd hid_data_cmd = {
+             .registerIndex = offsetof(struct i2c_hid_desc, wDataRegister),
+             .opcode = 0x00,
+             .length = 2 };
+/* write output reports */
+static const struct i2c_hid_cmd hid_out_cmd = {
+             .registerIndex = offsetof(struct i2c_hid_desc,
+                     wOutputRegister),
+             .opcode = 0x00,
+             .length = 2 };
+
+/* The main device structure */
+struct i2c_hid {
+     struct i2c_client       *client;        /* i2c client */
+     struct hid_device       *hid;   /* pointer to corresponding HID dev */
+     union {
+             __u8 hdesc_buffer[sizeof(struct i2c_hid_desc)];
+             struct i2c_hid_desc hdesc;      /* the HID Descriptor */
+     };
+     __le16                  wHIDDescRegister; /* location of the i2c
+                                                * register of the HID
+                                                * descriptor. */
+     unsigned int            bufsize;        /* i2c buffer size */
+     char                    *inbuf;         /* Input buffer */
+     char                    *cmdbuf;        /* Command buffer */
+     char                    *argsbuf;       /* Command arguments buffer */
+
+     unsigned long           flags;          /* device flags */
+
+     int                     irq;            /* the interrupt line irq */
+
+     wait_queue_head_t       wait;           /* For waiting the interrupt */
+};
+
+static int __i2c_hid_command(struct i2c_client *client,
+             const struct i2c_hid_cmd *command, u8 reportID,
+             u8 reportType, u8 *args, int args_len,
+             unsigned char *buf_recv, int data_len)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     union command *cmd = (union command *)ihid->cmdbuf;
+     int ret;
+     struct i2c_msg msg[2];
+     int msg_num = 1;
+
+     int length = command->length;
+     bool wait = command->wait;
+     unsigned int registerIndex = command->registerIndex;
+
+     /* special case for hid_descr_cmd */
+     if (command == &hid_descr_cmd) {
+             cmd->c.reg = ihid->wHIDDescRegister;
+     } else {
+             cmd->data[0] = ihid->hdesc_buffer[registerIndex];
+             cmd->data[1] = ihid->hdesc_buffer[registerIndex + 1];
+     }
+
+     if (length > 2) {
+             cmd->c.opcode = command->opcode;
+             cmd->c.reportTypeID = reportID | reportType << 4;
+     }
+
+     memcpy(cmd->data + length, args, args_len);
+     length += args_len;
+
+     i2c_hid_dbg(ihid, "%s: cmd=%*ph\n", __func__, length, cmd->data);
+
+     msg[0].addr = client->addr;
+     msg[0].flags = client->flags & I2C_M_TEN;
+     msg[0].len = length;
+     msg[0].buf = cmd->data;
+     if (data_len > 0) {
+             msg[1].addr = client->addr;
+             msg[1].flags = client->flags & I2C_M_TEN;
+             msg[1].flags |= I2C_M_RD;
+             msg[1].len = data_len;
+             msg[1].buf = buf_recv;
+             msg_num = 2;
+             set_bit(I2C_HID_READ_PENDING, &ihid->flags);
+     }
+
+     if (wait)
+             set_bit(I2C_HID_RESET_PENDING, &ihid->flags);
+
+     ret = i2c_transfer(client->adapter, msg, msg_num);
+
+     if (data_len > 0)
+             clear_bit(I2C_HID_READ_PENDING, &ihid->flags);
+
+     if (ret != msg_num)
+             return ret < 0 ? ret : -EIO;
+
+     ret = 0;
+
+     if (wait) {
+             i2c_hid_dbg(ihid, "%s: waiting...\n", __func__);
+             if (!wait_event_timeout(ihid->wait,
+                             !test_bit(I2C_HID_RESET_PENDING, &ihid->flags),
+                             msecs_to_jiffies(5000)))
+                     ret = -ENODATA;
+             i2c_hid_dbg(ihid, "%s: finished.\n", __func__);
+     }
+
+     return ret;
+}
+
+static int i2c_hid_command(struct i2c_client *client,
+             const struct i2c_hid_cmd *command,
+             unsigned char *buf_recv, int data_len)
+{
+     return __i2c_hid_command(client, command, 0, 0, NULL, 0,
+                             buf_recv, data_len);
+}
+
+static int i2c_hid_get_report(struct i2c_client *client, u8 reportType,
+             u8 reportID, unsigned char *buf_recv, int data_len)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     u8 args[3];
+     int ret;
+     int args_len = 0;
+     u16 readRegister = le16_to_cpu(ihid->hdesc.wDataRegister);
+
+     i2c_hid_dbg(ihid, "%s\n", __func__);
+
+     if (reportID >= 0x0F) {
+             args[args_len++] = reportID;
+             reportID = 0x0F;
+     }
+
+     args[args_len++] = readRegister & 0xFF;
+     args[args_len++] = readRegister >> 8;
+
+     ret = __i2c_hid_command(client, &hid_get_report_cmd, reportID,
+             reportType, args, args_len, buf_recv, data_len);
+     if (ret) {
+             dev_err(&client->dev, "hid_get_report_cmd Fail\n");

                How about "failed to retrieve report from device.\n"?

quoted

+             return -EINVAL;
+     }
+
+     return 0;
+}
+
+static int i2c_hid_set_report(struct i2c_client *client, u8 reportType,
+             u8 reportID, unsigned char *buf, size_t data_len)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     u8 *args = ihid->argsbuf;
+     int ret;
+     u16 dataRegister = le16_to_cpu(ihid->hdesc.wDataRegister);
+     int args_len =  (reportID >= 0x0F ? 1 : 0) +
+                     2 /* dataRegister */ +
+                     2 /* data_len */ +
+                     data_len;
+     int index = 0;
+
+     i2c_hid_dbg(ihid, "%s\n", __func__);
+
+     if (reportID >= 0x0F) {
+             args[index++] = reportID;
+             reportID = 0x0F;
+     }
+
+     args[index++] = dataRegister & 0xFF;
+     args[index++] = dataRegister >> 8;
+
+     /* hidraw already checked that data_len < HID_MAX_BUFFER_SIZE */
+     args[index++] = data_len & 0xFF;
+     args[index++] = (data_len >> 8) & 0xFF;
+
+     memcpy(&args[index], buf, data_len);
+
+     ret = __i2c_hid_command(client, &hid_set_report_cmd, reportID,
+             reportType, args, args_len, NULL, 0);
+     if (ret) {
+             dev_err(&client->dev, "hid_set_report_cmd Fail\n");

                How about "failed to set a report to device.\n"?

quoted

+             return -EINVAL;
+     }
+
+     return data_len;
+}
+
+static int i2c_hid_write_out_report(struct i2c_client *client,
+             u8 reportID, unsigned char *buf, size_t data_len)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     u8 *args = ihid->argsbuf;
+     int ret;
+     int args_len =  1 /* reportID */ +
+                     2 /* data_len */ +
+                     data_len;
+     int index = 0;
+
+     i2c_hid_dbg(ihid, "%s\n", __func__);
+
+     args[index++] = reportID;
+
+     /* hidraw already checked that data_len < HID_MAX_BUFFER_SIZE */
+     args[index++] = data_len & 0xFF;
+     args[index++] = (data_len >> 8) & 0xFF;
+
+     memcpy(&args[index], buf, data_len);
+
+     ret = __i2c_hid_command(client, &hid_out_cmd, 0, 0, args, args_len,
+             NULL, 0);
+     if (ret) {
+             dev_err(&client->dev, "hid_out_cmd Fail\n");

                How about "failed to write output report.\n"?

quoted

+             return -EINVAL;
+     }
+
+     return data_len;
+}
+
+static int i2c_hid_set_power(struct i2c_client *client, int power_state)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret;
+
+     i2c_hid_dbg(ihid, "%s\n", __func__);
+
+     ret = __i2c_hid_command(client, &hid_set_power_cmd, power_state,
+             0, NULL, 0, NULL, 0);
+     if (ret)
+             dev_err(&client->dev, "hid_set_power_cmd Fail\n");

                How about "failed to change power setting.\n"?

quoted

+
+     return ret;
+}
+
+static int i2c_hid_hwreset(struct i2c_client *client)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret;
+
+     i2c_hid_dbg(ihid, "%s\n", __func__);
+
+     ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
+     if (ret)
+             return ret;
+
+     i2c_hid_dbg(ihid, "resetting...\n");
+
+     ret = i2c_hid_command(client, &hid_reset_cmd, NULL, 0);
+     if (ret) {
+             dev_err(&client->dev, "hid_reset_cmd Fail\n");

                How about "failed to reset device.\n"?

quoted

+             i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
+             return ret;
+     }
+
+     return 0;
+}
+
+static int i2c_hid_get_input(struct i2c_hid *ihid)
+{
+     int ret, ret_size;
+     int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);
+
+     ret = i2c_master_recv(ihid->client, ihid->inbuf, size);
+     if (ret != size) {
+             if (ret < 0)
+                     return ret;
+
+             dev_err(&ihid->client->dev, "%s: got %d data instead of %d\n",
+                     __func__, ret, size);
+             return ret;
+     }
+
+     ret_size = ihid->inbuf[0] | ihid->inbuf[1] << 8;
+
+     if (!ret_size) {
+             /* host or device initiated RESET completed */
+             if (test_and_clear_bit(I2C_HID_RESET_PENDING, &ihid->flags))
+                     wake_up(&ihid->wait);
+             return 0;
+     }
+
+     if (ret_size > size) {
+             dev_err(&ihid->client->dev, "%s: incomplete report (%d/%d)\n",
+                     __func__, size, ret_size);
+             return -EIO;
+     }
+
+     i2c_hid_dbg(ihid, "input: %*ph\n", ret_size, ihid->inbuf);
+
+     if (test_bit(I2C_HID_STARTED, &ihid->flags))
+             hid_input_report(ihid->hid, HID_INPUT_REPORT, ihid->inbuf + 2,
+                             ret_size - 2, 1);
+
+     return 0;
+}
+
+static irqreturn_t i2c_hid_irq(int irq, void *dev_id)
+{
+     struct i2c_hid *ihid = dev_id;
+
+     if (test_bit(I2C_HID_READ_PENDING, &ihid->flags))
+             return IRQ_HANDLED;
+
+     i2c_hid_get_input(ihid);
+
+     return IRQ_HANDLED;
+}
+
+static int i2c_hid_get_report_length(struct hid_report *report)
+{
+     return ((report->size - 1) >> 3) + 1 +
+             report->device->report_enum[report->type].numbered + 2;
+}
+
+static void i2c_hid_init_report(struct hid_report *report, u8 *buffer,
+     size_t bufsize)
+{
+     struct hid_device *hid = report->device;
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     unsigned int size, ret_size;
+
+     size = i2c_hid_get_report_length(report);
+     i2c_hid_get_report(client,
+                     report->type == HID_FEATURE_REPORT ? 0x03 : 0x01,
+                     report->id, buffer, size);
+
+     i2c_hid_dbg(ihid, "report (len=%d): %*ph\n", size, size, ihid->inbuf);
+
+     ret_size = buffer[0] | (buffer[1] << 8);
+
+     if (ret_size != size) {
+             dev_err(&client->dev, "error in %s size:%d / ret_size:%d\n",
+                     __func__, size, ret_size);
+             return;
+     }
+
+     /* hid->driver_lock is held as we are in probe function,
+      * we just need to setup the input fields, so using
+      * hid_report_raw_event is safe. */
+     hid_report_raw_event(hid, report->type, buffer + 2, size - 2, 1);
+}
+
+/*
+ * Initialize all reports
+ */
+static void i2c_hid_init_reports(struct hid_device *hid)
+{
+     struct hid_report *report;
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     u8 *inbuf = kzalloc(ihid->bufsize, GFP_KERNEL);
+
+     if (!inbuf)
+             return;
+
+     list_for_each_entry(report,
+             &hid->report_enum[HID_INPUT_REPORT].report_list, list)
+             i2c_hid_init_report(report, inbuf, ihid->bufsize);
+
+     list_for_each_entry(report,
+             &hid->report_enum[HID_FEATURE_REPORT].report_list, list)
+             i2c_hid_init_report(report, inbuf, ihid->bufsize);
+
+     kfree(inbuf);
+}
+
+/*
+ * Traverse the supplied list of reports and find the longest
+ */
+static void i2c_hid_find_max_report(struct hid_device *hid, unsigned int type,
+             unsigned int *max)
+{
+     struct hid_report *report;
+     unsigned int size;
+
+     /* We should not rely on wMaxInputLength, as some devices may set it to
+      * a wrong length. */
+     list_for_each_entry(report, &hid->report_enum[type].report_list, list) {
+             size = i2c_hid_get_report_length(report);
+             if (*max < size)
+                     *max = size;
+     }
+}
+
+static int i2c_hid_alloc_buffers(struct i2c_hid *ihid)
+{
+     /* the worst case is computed from the set_report command with a
+      * reportID > 15 and the maximum report length */
+     int args_len = sizeof(__u8) + /* optional ReportID byte */
+                    sizeof(__u16) + /* data register */
+                    sizeof(__u16) + /* size of the report */
+                    ihid->bufsize; /* report */
+
+     ihid->inbuf = kzalloc(ihid->bufsize, GFP_KERNEL);
+
+     if (!ihid->inbuf)
+             return -ENOMEM;
+
+     ihid->argsbuf = kzalloc(args_len, GFP_KERNEL);
+
+     if (!ihid->argsbuf) {
+             kfree(ihid->inbuf);
+             return -ENOMEM;
+     }
+
+     ihid->cmdbuf = kzalloc(sizeof(union command) + args_len, GFP_KERNEL);
+
+     if (!ihid->cmdbuf) {
+             kfree(ihid->inbuf);
+             kfree(ihid->argsbuf);
+             return -ENOMEM;
+     }
+
+     return 0;
+}
+
+static void i2c_hid_free_buffers(struct i2c_hid *ihid)
+{
+     kfree(ihid->inbuf);
+     kfree(ihid->argsbuf);
+     kfree(ihid->cmdbuf);
+     ihid->inbuf = NULL;
+     ihid->cmdbuf = NULL;
+     ihid->argsbuf = NULL;
+}
+
+static int i2c_hid_get_raw_report(struct hid_device *hid,
+             unsigned char report_number, __u8 *buf, size_t count,
+             unsigned char report_type)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret;
+
+     if (count > ihid->bufsize)
+             count = ihid->bufsize;
+
+     ret = i2c_hid_get_report(client,
+                     report_type == HID_FEATURE_REPORT ? 0x03 : 0x01,
+                     report_number, ihid->inbuf, count);
+
+     if (ret < 0)
+             return ret;
+
+     count = ihid->inbuf[0] | (ihid->inbuf[1] << 8);
+
+     memcpy(buf, ihid->inbuf + 2, count);
+
+     return count;
+}
+
+static int i2c_hid_output_raw_report(struct hid_device *hid, __u8 *buf,
+             size_t count, unsigned char report_type)
+{
+     struct i2c_client *client = hid->driver_data;
+     int report_id = buf[0];
+
+     if (report_type == HID_OUTPUT_REPORT)
+             return i2c_hid_write_out_report(client, report_id, buf, count);
+
+     return i2c_hid_set_report(client,
+                             report_type == HID_FEATURE_REPORT ? 0x03 : 0x01,
+                             report_id, buf, count);
+}
+
+static int i2c_hid_parse(struct hid_device *hid)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     struct i2c_hid_desc *hdesc = &ihid->hdesc;
+     unsigned int rsize;
+     char *rdesc;
+     int ret;
+     int tries = 3;
+
+     i2c_hid_dbg(ihid, "entering %s\n", __func__);
+
+     rsize = le16_to_cpu(hdesc->wReportDescLength);
+     if (!rsize || rsize > HID_MAX_DESCRIPTOR_SIZE) {
+             dbg_hid("weird size of report descriptor (%u)\n", rsize);
+             return -EINVAL;
+     }
+
+     do {
+             ret = i2c_hid_hwreset(client);
+             if (ret)
+                     msleep(1000);
+     } while (tries-- > 0 && ret);
+
+     if (ret)
+             return ret;
+
+     rdesc = kzalloc(rsize, GFP_KERNEL);
+
+     if (!rdesc) {
+             dbg_hid("couldn't allocate rdesc memory\n");
+             return -ENOMEM;
+     }
+
+     i2c_hid_dbg(ihid, "asking HID report descriptor\n");
+
+     ret = i2c_hid_command(client, &hid_report_descr_cmd, rdesc, rsize);
+     if (ret) {
+             hid_err(hid, "reading report descriptor failed\n");
+             kfree(rdesc);
+             return -EIO;
+     }
+
+     i2c_hid_dbg(ihid, "Report Descriptor: %*ph\n", rsize, rdesc);
+
+     ret = hid_parse_report(hid, rdesc, rsize);
+     kfree(rdesc);
+     if (ret) {
+             dbg_hid("parsing report descriptor failed\n");
+             return ret;
+     }
+
+     return 0;
+}
+
+static int i2c_hid_start(struct hid_device *hid)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret;
+     int old_bufsize = ihid->bufsize;
+
+     ihid->bufsize = HID_MIN_BUFFER_SIZE;
+     i2c_hid_find_max_report(hid, HID_INPUT_REPORT, &ihid->bufsize);
+     i2c_hid_find_max_report(hid, HID_OUTPUT_REPORT, &ihid->bufsize);
+     i2c_hid_find_max_report(hid, HID_FEATURE_REPORT, &ihid->bufsize);
+
+     if (ihid->bufsize > old_bufsize || !ihid->inbuf || !ihid->cmdbuf) {
+             i2c_hid_free_buffers(ihid);
+
+             ret = i2c_hid_alloc_buffers(ihid);
+
+             if (ret)
+                     return ret;
+     }
+
+     if (!(hid->quirks & HID_QUIRK_NO_INIT_REPORTS))
+             i2c_hid_init_reports(hid);
+
+     return 0;
+}
+
+static void i2c_hid_stop(struct hid_device *hid)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+
+     hid->claimed = 0;
+
+     i2c_hid_free_buffers(ihid);
+}
+
+static int i2c_hid_open(struct hid_device *hid)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret;
+
+     if (!hid->open++) {
+             ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
+             if (ret) {
+                     hid->open--;
+                     return -EIO;
+             }
+             set_bit(I2C_HID_STARTED, &ihid->flags);
+     }
+     return 0;
+}
+
+static void i2c_hid_close(struct hid_device *hid)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+
+     /* protecting hid->open to make sure we don't restart
+      * data acquistion due to a resumption we no longer
+      * care about
+      */
+     if (!--hid->open) {
+             clear_bit(I2C_HID_STARTED, &ihid->flags);
+
+             /* Save some power */
+             i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
+     }
+}
+
+static int i2c_hid_power(struct hid_device *hid, int lvl)
+{
+     struct i2c_client *client = hid->driver_data;
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret = 0;
+
+     i2c_hid_dbg(ihid, "%s lvl:%d\n", __func__, lvl);
+
+     switch (lvl) {
+     case PM_HINT_FULLON:
+             ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
+             break;
+     case PM_HINT_NORMAL:
+             ret = i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
+             break;
+     }
+     return ret;
+}
+
+static int i2c_hid_hidinput_input_event(struct input_dev *dev,
+             unsigned int type, unsigned int code, int value)
+{
+     struct hid_device *hid = input_get_drvdata(dev);
+     struct hid_field *field;
+     int offset;
+
+     if (type == EV_FF)
+             return input_ff_event(dev, type, code, value);
+
+     if (type != EV_LED)
+             return -1;
+
+     offset = hidinput_find_field(hid, type, code, &field);
+
+     if (offset == -1) {
+             hid_warn(dev, "event field not found\n");
+             return -1;
+     }
+
+     hid_set_field(field, offset, value);
+
+     return 0;
+}
+
+static struct hid_ll_driver i2c_hid_ll_driver = {
+     .parse = i2c_hid_parse,
+     .start = i2c_hid_start,
+     .stop = i2c_hid_stop,
+     .open = i2c_hid_open,
+     .close = i2c_hid_close,
+     .power = i2c_hid_power,
+     .hidinput_input_event = i2c_hid_hidinput_input_event,
+};
+
+static int __devinit i2c_hid_init_irq(struct i2c_client *client)
+{
+     struct i2c_hid *ihid = i2c_get_clientdata(client);
+     int ret;
+
+     dev_dbg(&client->dev, "Requesting IRQ: %d\n", client->irq);
+
+     ret = request_threaded_irq(client->irq, NULL, i2c_hid_irq,
+                     IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+                     client->name, ihid);
+     if (ret < 0) {
+             dev_dbg(&client->dev,
+                     "Could not register for %s interrupt, irq = %d,"
+                     " ret = %d\n",
+             client->name, client->irq, ret);
+
+             return ret;
+     }
+
+     ihid->irq = client->irq;
+
+     return 0;
+}
+
+static int __devinit i2c_hid_fetch_hid_descriptor(struct i2c_hid *ihid)
+{
+     struct i2c_client *client = ihid->client;
+     struct i2c_hid_desc *hdesc = &ihid->hdesc;
+     unsigned int dsize;
+     int ret;
+
+     /* Fetch the length of HID description, retrieve the 4 first bytes:
+      * bytes 0-1 -> length
+      * bytes 2-3 -> bcdVersion (has to be 1.00) */
+     ret = i2c_hid_command(client, &hid_descr_cmd, ihid->hdesc_buffer, 4);
+
+     i2c_hid_dbg(ihid, "%s, ihid->hdesc_buffer: %*ph\n",
+                     __func__, 4, ihid->hdesc_buffer);
+
+     if (ret) {
+             dev_err(&client->dev, "HID_DESCR_LENGTH_CMD Fail (ret=%d)\n",

                How about "failed to get descriptor length (ret = %d).\n"?

quoted

+                     ret);
+             return -ENODEV;

                In this function, would it be more approriate to return -EINVAL?

quoted

+     }
+
+     dsize = le16_to_cpu(hdesc->wHIDDescLength);
+     if (!dsize || dsize > HID_MAX_DESCRIPTOR_SIZE) {
+             dev_err(&client->dev, "weird size of HID descriptor (%u)\n",
+                     dsize);
+             return -ENODEV;

                       -EINVAL?

quoted

+     }
+
+     /* check bcdVersion == 1.0 */
+     if (le16_to_cpu(hdesc->bcdVersion) != 0x0100) {
+             dev_err(&client->dev,
+                     "unexpected HID descriptor bcdVersion (0x%04x)\n",
+                     le16_to_cpu(hdesc->bcdVersion));
+             return -ENODEV;

                       -EINVAL?

quoted

+     }
+
+     i2c_hid_dbg(ihid, "Fetching the HID descriptor\n");
+
+     ret = i2c_hid_command(client, &hid_descr_cmd, ihid->hdesc_buffer,
+                             dsize);
+     if (ret) {
+             dev_err(&client->dev, "hid_descr_cmd Fail\n");

                How about "failed to fetch HID descriptor.\n"?

quoted

+             return -ENODEV;

                       -EINVAL?

Thanks,
-JJ

quoted

+     }
+
+     i2c_hid_dbg(ihid, "HID Descriptor: %*ph\n", dsize, ihid->hdesc_buffer);
+
+     return 0;
+}
+