2 files changed, 201 insertions, 30 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-hid-logitech-lg4ff b/Documentation/ABI/testing/sysfs-driver-hid-logitech-lg4ff
index 60f24a1d8119..b3f6a2ac5007 100644
--- a/Documentation/ABI/testing/sysfs-driver-hid-logitech-lg4ff
+++ b/Documentation/ABI/testing/sysfs-driver-hid-logitech-lg4ff
@@ -15,7 +15,32 @@ Description:	Displays a set of alternate modes supported by a wheel. Each
                   Tag: Mode Name
                 Currently active mode is marked with an asterisk. List also
                 contains an abstract item "native" which always denotes the
-                native mode of the wheel.
+                native mode of the wheel. Echoing the mode tag switches the
+                wheel into the corresponding mode. Depending on the exact model
+                of the wheel not all listed modes might always be selectable.
+                If a wheel cannot be switched into the desired mode, -EINVAL
+                is returned accompanied with an explanatory message in the
+                kernel log.
+                This entry is not created for devices that have only one mode.
+
+                Currently supported mode switches:
+                Driving Force Pro:
+                  DF-EX --> DFP
+
+                G25:
+                  DF-EX --> DFP --> G25
+
+                G27:
+                  DF-EX <*> DFP <-> G25 <-> G27
+                  DF-EX <*--------> G25 <-> G27
+                  DF-EX <*----------------> G27
+
+                DFGT:
+                  DF-EX <*> DFP <-> DFGT
+                  DF-EX <*--------> DFGT
+
+                * hid_logitech module must be loaded with lg4ff_no_autoswitch=1
+                  parameter set in order for the switch to DF-EX mode to work.
 
 What:           /sys/bus/hid/drivers/logitech/<dev>/real_id
 Date:           Feb 2015
diff --git a/drivers/hid/hid-lg4ff.c b/drivers/hid/hid-lg4ff.c
index dd307724965f..854982be3194 100644
--- a/drivers/hid/hid-lg4ff.c
+++ b/drivers/hid/hid-lg4ff.c
@@ -201,26 +201,47 @@ static const struct lg4ff_wheel_ident_checklist lg4ff_main_checklist = {
 };
 
 /* Compatibility mode switching commands */
-static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_dfp = {
-        1,
-        {0xf8, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00}
+/* EXT_CMD9 - Understood by G27 and DFGT */
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext09_dfex = {
+        2,
+        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* Revert mode upon USB reset */
+         0xf8, 0x09, 0x00, 0x01, 0x00, 0x00, 0x00}      /* Switch mode to DF-EX with detach */
 };
 
-static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_dfgt = {
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext09_dfp = {
         2,
-        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* 1st command */
-         0xf8, 0x09, 0x03, 0x01, 0x00, 0x00, 0x00}      /* 2nd command */
+        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* Revert mode upon USB reset */
+         0xf8, 0x09, 0x01, 0x01, 0x00, 0x00, 0x00}      /* Switch mode to DFP with detach */
 };
 
-static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_g25 = {
-        1,
-        {0xf8, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00}
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext09_g25 = {
+        2,
+        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* Revert mode upon USB reset */
+         0xf8, 0x09, 0x02, 0x01, 0x00, 0x00, 0x00}      /* Switch mode to G25 with detach */
 };
 
-static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_g27 = {
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext09_dfgt = {
         2,
-        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* 1st command */
-         0xf8, 0x09, 0x04, 0x01, 0x00, 0x00, 0x00}      /* 2nd command */
+        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* Revert mode upon USB reset */
+         0xf8, 0x09, 0x03, 0x01, 0x00, 0x00, 0x00}      /* Switch mode to DFGT with detach */
+};
+
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext09_g27 = {
+        2,
+        {0xf8, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00,      /* Revert mode upon USB reset */
+         0xf8, 0x09, 0x04, 0x01, 0x00, 0x00, 0x00}      /* Switch mode to G27 with detach */
+};
+
+/* EXT_CMD1 - Understood by DFP, G25, G27 and DFGT */
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext01_dfp = {
+        1,
+        {0xf8, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00}
+};
+
+/* EXT_CMD16 - Understood by G25 and G27 */
+static const struct lg4ff_compat_mode_switch lg4ff_mode_switch_ext16_g25 = {
+        1,
+        {0xf8, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00}
 };
 
 /* Recalculates X axis value accordingly to currently selected range */
@@ -489,6 +510,63 @@ static void hid_lg4ff_set_range_dfp(struct hid_device *hid, __u16 range)
         hid_hw_request(hid, report, HID_REQ_SET_REPORT);
 }
 
+static const struct lg4ff_compat_mode_switch *lg4ff_get_mode_switch_command(const u16 real_product_id, const u16 target_product_id)
+{
+        switch (real_product_id) {
+        case USB_DEVICE_ID_LOGITECH_DFP_WHEEL:
+                switch (target_product_id) {
+                case USB_DEVICE_ID_LOGITECH_DFP_WHEEL:
+                        return &lg4ff_mode_switch_ext01_dfp;
+                /* DFP can only be switched to its native mode */
+                default:
+                        return NULL;
+                }
+                break;
+        case USB_DEVICE_ID_LOGITECH_G25_WHEEL:
+                switch (target_product_id) {
+                case USB_DEVICE_ID_LOGITECH_DFP_WHEEL:
+                        return &lg4ff_mode_switch_ext01_dfp;
+                case USB_DEVICE_ID_LOGITECH_G25_WHEEL:
+                        return &lg4ff_mode_switch_ext16_g25;
+                /* G25 can only be switched to DFP mode or its native mode */
+                default:
+                        return NULL;
+                }
+                break;
+        case USB_DEVICE_ID_LOGITECH_G27_WHEEL:
+                switch (target_product_id) {
+                case USB_DEVICE_ID_LOGITECH_WHEEL:
+                        return &lg4ff_mode_switch_ext09_dfex;
+                case USB_DEVICE_ID_LOGITECH_DFP_WHEEL:
+                        return &lg4ff_mode_switch_ext09_dfp;
+                case USB_DEVICE_ID_LOGITECH_G25_WHEEL:
+                        return &lg4ff_mode_switch_ext09_g25;
+                case USB_DEVICE_ID_LOGITECH_G27_WHEEL:
+                        return &lg4ff_mode_switch_ext09_g27;
+                /* G27 can only be switched to DF-EX, DFP, G25 or its native mode */
+                default:
+                        return NULL;
+                }
+                break;
+        case USB_DEVICE_ID_LOGITECH_DFGT_WHEEL:
+                switch (target_product_id) {
+                case USB_DEVICE_ID_LOGITECH_WHEEL:
+                        return &lg4ff_mode_switch_ext09_dfex;
+                case USB_DEVICE_ID_LOGITECH_DFP_WHEEL:
+                        return &lg4ff_mode_switch_ext09_dfp;
+                case USB_DEVICE_ID_LOGITECH_DFGT_WHEEL:
+                        return &lg4ff_mode_switch_ext09_dfgt;
+                /* DFGT can only be switched to DF-EX, DFP or its native mode */
+                default:
+                        return NULL;
+                }
+                break;
+        /* No other wheels have multiple modes */
+        default:
+                return NULL;
+        }
+}
+
 static int lg4ff_switch_compatibility_mode(struct hid_device *hid, const struct lg4ff_compat_mode_switch *s)
 {
         struct usb_device *usbdev = hid_to_usb_dev(hid);
@@ -558,7 +636,87 @@ static ssize_t lg4ff_alternate_modes_show(struct device *dev, struct device_attr
 
 static ssize_t lg4ff_alternate_modes_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
 {
-        return -ENOSYS;
+        struct hid_device *hid = to_hid_device(dev);
+        struct lg4ff_device_entry *entry;
+        struct lg_drv_data *drv_data;
+        const struct lg4ff_compat_mode_switch *s;
+        u16 target_product_id = 0;
+        int i, ret;
+        char *lbuf;
+
+        drv_data = hid_get_drvdata(hid);
+        if (!drv_data) {
+                hid_err(hid, "Private driver data not found!\n");
+                return -EINVAL;
+        }
+
+        entry = drv_data->device_props;
+        if (!entry) {
+                hid_err(hid, "Device properties not found!\n");
+                return -EINVAL;
+        }
+
+        /* Allow \n at the end of the input parameter */
+        lbuf = kasprintf(GFP_KERNEL, "%s", buf);
+        if (!lbuf)
+                return -ENOMEM;
+
+        i = strlen(lbuf);
+        if (lbuf[i-1] == '\n') {
+                if (i == 1) {