On Thu, 6 Sep 2012, Dmitry Torokhov wrote: > > Hi list, > > I have a tablet that shows it is a HID device. > > But the report descriptor looks broken. > > > > Below shows the device information: > > > > lsusb -v: > > > > Bus 002 Device 004: ID 04b4:3045 Cypress Semiconductor Corp. > > Device Descriptor: > > bLength 18 > > bDescriptorType 1 > > bcdUSB 1.10 > > bDeviceClass 0 (Defined at Interface level) > > bDeviceSubClass 0 > > bDeviceProtocol 0 > > bMaxPacketSize0 8 > > idVendor 0x04b4 Cypress Semiconductor Corp. > > idProduct 0x3045 > > bcdDevice 1.00 > > iManufacturer 1 Ping-IT > > iProduct 2 RS232_USB > > iSerial 0 > > bNumConfigurations 1 > > Configuration Descriptor: > > bLength 9 > > bDescriptorType 2 > > wTotalLength 34 > > bNumInterfaces 1 > > bConfigurationValue 1 > > iConfiguration 3 Bus power > > bmAttributes 0xa0 > > (Bus Powered) > > Remote Wakeup > > MaxPower 100mA > > Interface Descriptor: > > bLength 9 > > bDescriptorType 4 > > bInterfaceNumber 0 > > bAlternateSetting 0 > > bNumEndpoints 1 > > bInterfaceClass 3 Human Interface Device > > bInterfaceSubClass 0 No Subclass > > bInterfaceProtocol 0 None > > iInterface 4 HID > > HID Device Descriptor: > > bLength 9 > > bDescriptorType 33 > > bcdHID 1.10 > > bCountryCode 0 Not supported > > bNumDescriptors 1 > > bDescriptorType 34 Report > > wDescriptorLength 26 > > Report Descriptors: > > ** UNAVAILABLE ** > > Endpoint Descriptor: > > bLength 7 > > bDescriptorType 5 > > bEndpointAddress 0x81 EP 1 IN > > bmAttributes 3 > > Transfer Type Interrupt > > Synch Type None > > Usage Type Data > > wMaxPacketSize 0x0008 1x 8 bytes > > bInterval 10 > > Device Status: 0x0000 > > (Bus Powered) > > > > And below is the report descriptor ( by usbhid-dump / hidrd-convert ) > > > > 0x05, 0x0D, /* Usage Page (Digitizer), */ > > 0x09, 0x08, /* Usage (3D Digitizer), */ > > 0xA1, 0x01, /* Collection (Application), */ > > 0x09, 0x01, /* Usage (Digitizer), */ > > 0xA1, 0x00, /* Collection (Physical), */ > > 0x05, 0x01, /* Usage Page (Desktop), */ > > 0x09, 0x3B, /* Usage (Byte Count), */ > > 0x15, 0x00, /* Logical Minimum (0), */ > > 0x25, 0x7F, /* Logical Maximum (127), */ > > 0x75, 0x08, /* Report Size (8), */ > > 0x95, 0x07, /* Report Count (7), */ > > 0x81, 0x02, /* Input (Variable), */ > > 0xC0, /* End Collection, */ > > 0xC0 /* End Collection */ > > > > The report descriptor looks broken to me: > > 1. The report descriptor does not have Usage for TOOL_PEN/STYLUS/STYLUS2/PRESSURE, > > so evdev doest not recognized it as a tablet. > > Actually, the report descriptor does not define any detail of the data. > > It only shows a 7 bytes report content. > > 2. It does not have Report ID field. > > (Does it make sense to have a report descriptor without Report ID field?) > > > > So in this case, should I implement a HID (special device) driver or > > a input driver (in drivers/input/tablet folder) for this device? > > > > I think because the driver would hardly use any of HID infrastructure it > would make sense to do it as an input driver. Agreed. It however also slightly depends on the actual data it is sending. It might be a proper HID protocol in the end, just the report descriptor might be completely bogus. We already have a couple devices supported in linux by hid-waltop driver. The only thing it does is that it replaces completely wrong report desriptor with a proper one, and it's enough to make the device work properly. But that really depends on the protocol that the device is using in the reports. -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
