On Thu, 2022-08-25 at 16:47 -0400, Peter F. Patel-Schneider wrote: > This patch will cause more use of a part of the driver that > constructs > messages that do not conform to the HID++ 2.0 specification. This > makes now a good time to fix the parts of the driver that construct > non-conforming messages. More information follows. > > > The Logitech HID++2.0 Draft Specification at > https://lekensteyn.nl/files/logitech/logitech_hidpp_2.0_specification_draft_2012-06-04.pdf > specifies (on pages 2 and 3) that the low-order nibble of the > function > (command) byte is non-zero. > > The HID++ driver at > https://github.com/torvalds/linux/blob/master/drivers/hid/hid-logitech-hidpp.c > has 1 in that nibble for some commands, > > #define CMD_ROOT_GET_FEATURE 0x01 > #define CMD_ROOT_GET_PROTOCOL_VERSION 0x11 > > #define CMD_GET_DEVICE_NAME_TYPE_GET_COUNT 0x01 > #define CMD_GET_DEVICE_NAME_TYPE_GET_DEVICE_NAME 0x11 > #define CMD_GET_DEVICE_NAME_TYPE_GET_TYPE 0x21 > > But other commands have zero in that nibble, namely > > #define CMD_BATTERY_LEVEL_STATUS_GET_BATTERY_LEVEL_STATUS 0x00 > #define CMD_BATTERY_LEVEL_STATUS_GET_BATTERY_CAPABILITY 0x10 > > #define CMD_BATTERY_VOLTAGE_GET_BATTERY_VOLTAGE 0x00 > > #define CMD_UNIFIED_BATTERY_GET_CAPABILITIES 0x00 > #define CMD_UNIFIED_BATTERY_GET_STATUS 0x10 > > #define CMD_HI_RESOLUTION_SCROLLING_SET_HIGHRES_SCROLLING_MODE 0x10 > > #define CMD_HIRES_WHEEL_GET_WHEEL_CAPABILITY 0x00 > #define CMD_HIRES_WHEEL_SET_WHEEL_MODE 0x20 > > #define CMD_SOLAR_SET_LIGHT_MEASURE 0x00 > > #define CMD_TOUCHPAD_FW_ITEMS_SET 0x10 Sounds like none of those commands should have anything set in that lower nibble, but this patch should be enough to take care of either case. I don't know whether the "rap" commands are used at all for HID++ 2.0 commands, or just for HID++ 1.0. Is the software ID something random that the software in question chooses? I chose 0x06 as we're at Linux version 6.0... diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c index 86e7a38d8a9a..4c430b24b6bc 100644 --- a/drivers/hid/hid-logitech-hidpp.c +++ b/drivers/hid/hid-logitech-hidpp.c @@ -41,6 +41,9 @@ module_param(disable_tap_to_click, bool, 0644); MODULE_PARM_DESC(disable_tap_to_click, "Disable Tap-To-Click mode reporting for touchpads (only on the K400 currently)."); +/* Define a non-zero software ID to identify our own responses */ +#define LINUX_KERNEL_SW_ID 0x06 + #define REPORT_ID_HIDPP_SHORT 0x10 #define REPORT_ID_HIDPP_LONG 0x11 #define REPORT_ID_HIDPP_VERY_LONG 0x12 @@ -343,7 +346,7 @@ static int hidpp_send_fap_command_sync(struct hidpp_device *hidpp, else message->report_id = REPORT_ID_HIDPP_LONG; message->fap.feature_index = feat_index; - message->fap.funcindex_clientid = funcindex_clientid; + message->fap.funcindex_clientid = funcindex_clientid | LINUX_KERNEL_SW_ID; memcpy(&message->fap.params, params, param_count); ret = hidpp_send_message_sync(hidpp, message, response);
