Hello,
We are using the usbtouchscreen driver for a 0eef:0001 eGalax based device and
have observed cases were BTN_TOUCH seems to be stuck as release events are not
reported promptly. In those situations the release event is reported after
arbitrary time when the next touch event is triggered.
An usbmon trace shows that the problem occurs reproducible when the final 5
byte report containing the liftoff event finishes at an 8 byte boundary:
ceb81c80 1241543630 C Ii:1:002:1 0:4 16 = 81097c0a 5b81097c 0a5a8109 7b0a5a81
ceb81c80 1241543964 S Ii:1:002:1 -115:4 16 <
ceb81c80 1241555630 C Ii:1:002:1 0:4 16 = 097a0a5a 8109780a 59810975 0a578109
ceb81c80 1241555988 S Ii:1:002:1 -115:4 16 <
---[abort - urb gets unlinked]---
ceb81c80 1250629867 C Ii:1:002:1 -2:4 8 = 730a5380 09730a53
The usbtouchscreen driver is aware of both the report and diagnostic packets
supported by the controller. It enables multi frame support and defines the
report size for the eGalax to the 16 byte maximum diagnostic packet size
opposed to the 5 byte coordinate report.
In my opinion the situation described above is caused because the same size
definition is used for buffer allocation and interrupt endpoint requests to
the USB subsystem. The ehci-hcd will split the 16 byte request into up to 2
accesses according to the wMaxPacketSize of 8 byte for this endpoint. In case
the first transfer is answered by the eGalax with not less than the full 8 byte
requested, the host controller has got no way of knowing that the touch
controller will not have additional queued data until the next touch event.
As I am normally not involved into input drivers, please give me a hint to a
solution to this issue that would be acceptable for the maintainers and I can
prepare a tested patch accordingly.
Regards,
Christian
---
Bus 001 Device 002: ID 0eef:0001 D-WAV Scientific Co., Ltd eGalax TouchScreen
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x0eef D-WAV Scientific Co., Ltd
idProduct 0x0001 eGalax TouchScreen
bcdDevice 1.00
iManufacturer 1 eGalax Inc.
iProduct 2 USB TouchController
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 25
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 4 USB TouchScreen
bmAttributes 0xa0
(Bus Powered)
Remote Wakeup
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 255 Vendor Specific Subclass
bInterfaceProtocol 255 Vendor Specific Protocol
iInterface 0
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 5
Device Status: 0x0002
(Bus Powered)
Remote Wakeup Enabled
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 9 Hub
bDeviceSubClass 0 Unused
bDeviceProtocol 1 Single TT
bMaxPacketSize0 64
idVendor 0x1d6b Linux Foundation
idProduct 0x0002 2.0 root hub
bcdDevice 3.04
iManufacturer 3 Linux 3.4.61-rel_4_4002_0-svn216359 ehci_hcd
iProduct 2 Freescale On-Chip EHCI Host Controller
iSerial 1 fsl-ehci.0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 25
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xe0
Self Powered
Remote Wakeup
MaxPower 0mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 9 Hub
bInterfaceSubClass 0 Unused
bInterfaceProtocol 0 Full speed (or root) hub
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0004 1x 4 bytes
bInterval 12
Hub Descriptor:
bLength 9
bDescriptorType 41
nNbrPorts 1
wHubCharacteristic 0x0009
Per-port power switching
Per-port overcurrent protection
TT think time 8 FS bits
bPwrOn2PwrGood 10 * 2 milli seconds
bHubContrCurrent 0 milli Ampere
DeviceRemovable 0x00
PortPwrCtrlMask 0xff
Hub Port Status:
Port 1: 0000.0303 lowspeed power enable connect
Device Status: 0x0001
Self Powered
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