Add documentation to give a brief description on how to use the CCID Gadget Device. This includes a description for all attributes followed by an example on how to setup the device with ConfigFS. Signed-off-by: Marcus Folkesson <marcus.folkesson@xxxxxxxxx> --- Documentation/usb/gadget_ccid.rst | 267 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 267 insertions(+) create mode 100644 Documentation/usb/gadget_ccid.rst diff --git a/Documentation/usb/gadget_ccid.rst b/Documentation/usb/gadget_ccid.rst new file mode 100644 index 000000000000..5ac806b14604 --- /dev/null +++ b/Documentation/usb/gadget_ccid.rst @@ -0,0 +1,267 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============ +CCID Gadget +============ + +:Author: Marcus Folkesson <marcus.folkesson@xxxxxxxxx> + +Introduction +============ + +The CCID Gadget will present itself as a CCID device to the host system. +The device supports two endpoints for now; BULK IN and BULK OUT. +These endpoints is exposed to userspace via /dev/ccidg*. + +All CCID commands are sent on the BULK-OUT endpoint. Each command sent to the CCID +has an associated ending response. Some commands can also have intermediate +responses. The response is sent on the BULK-IN endpoint. +See Figure 3-3 in the CCID Specification [1]_ for more details. + +The CCID commands must be handled in userspace since the driver is only working +as a transport layer for the TPDUs. + + +CCID Commands +-------------- + +All CCID commands begins with a 10 bytes header followed by an optional +data field depending on message type. + ++--------+--------------+-------+----------------------------------+ +| Offset | Field | Size | Description | ++========+==============+=======+==================================+ +| 0 | bMessageType | 1 | Type of message | ++--------+--------------+-------+----------------------------------+ +| 1 | dwLength | 4 | Message specific data length | +| | | | | ++--------+--------------+-------+----------------------------------+ +| 5 | bSlot | 1 | Identifies the slot number | +| | | | for this command | ++--------+--------------+-------+----------------------------------+ +| 6 | bSeq | 1 | Sequence number for command | ++--------+--------------+-------+----------------------------------+ +| 7 | ... | 3 | Fields depends on message type | ++--------+--------------+-------+----------------------------------+ +| 10 | abData | array | Message specific data (OPTIONAL) | ++--------+--------------+-------+----------------------------------+ + + +Multiple CCID gadgets +---------------------- + +It is possible to create multiple instances of the CCID gadget, however, +a much more flexible way is to create one gadget and set the `nslots` attribute +to the number of desired CCID devices. + +All CCID commands specifies which slot that is the receiver in the `bSlot` field +of the CCID header. + +Usage +===== + +Access from userspace +---------------------- +All communication is by read(2) and write(2) to the corresponding /dev/ccidg* device. +Only one filedescriptor is allowed to be open to the device at a time. + +The buffer size provided to read(2) **must be at least** 522 (10 bytes header + 512 bytes payload) +bytes as we are working with whole commands. + +The buffer size provided to write(2) **may not exceed** 522 (10 bytes header + 512 bytes payload) +bytes as we are working with whole commands. + + +Configuration with configfs +---------------------------- + +ConfigFS is used to create and configure the CCID gadget. +In order to get a device to work as intended, a few attributes must +be considered. + +The attributes is described below followed by an example. + +features +~~~~~~~~~ + +The `feature` attribute writes to the dwFeatures field in the class descriptor. +See Table 5.1-1 Smart Card Device Descriptors in the CCID Specification [1]_. + +The value indicates what intelligent features the CCID has. +These values are available to user application as defines in ccid.h [2]_. +The default value is 0x00000000. + +The value is a bitwise OR operation performed on the following values: + ++------------+----------------------------------------------------------------+ +| Value | Description | ++============+================================================================+ +| 0x00000000 | No special characteristics | ++------------+----------------------------------------------------------------+ +| 0x00000002 | Automatic parameter configuration based on ATR data | ++------------+----------------------------------------------------------------+ +| 0x00000004 | Automatic activation of ICC on inserting | ++------------+----------------------------------------------------------------+ +| 0x00000008 | Automatic ICC voltage selection | ++------------+----------------------------------------------------------------+ +| 0x00000010 | Automatic ICC clock frequency change according to active | +| | parameters provided by the Host or self determined | ++------------+----------------------------------------------------------------+ +| 0x00000020 | Automatic baud rate change according to active | +| | parameters provided by the Host or self determined | ++------------+----------------------------------------------------------------+ +| 0x00000040 | Automatic parameters negotiation made by the CCID | ++------------+----------------------------------------------------------------+ +| 0x00000080 | Automatic PPS made by the CCID according to the | +| | active parameters | ++------------+----------------------------------------------------------------+ +| 0x00000100 | CCID can set ICC in clock stop mode | ++------------+----------------------------------------------------------------+ +| 0x00000200 | NAD value other than 00 accepted (T=1 protocol in use) | ++------------+----------------------------------------------------------------+ +| 0x00000400 | Automatic IFSD exchange as first exchange | ++------------+----------------------------------------------------------------+ + + +Only one of the following values may be present to select a level of exchange: + ++------------+--------------------------------------------------+ +| Value | Description | ++============+==================================================+ +| 0x00010000 | TPDU level exchanges with CCID | ++------------+--------------------------------------------------+ +| 0x00020000 | Short APDU level exchange with CCID | ++------------+--------------------------------------------------+ +| 0x00040000 | Short and Extended APDU level exchange with CCID | ++------------+--------------------------------------------------+ + +If none of those values is indicated the level of exchange is +character. + + +protocols +~~~~~~~~~~ +The `protocols` attribute writes to the dwProtocols field in the class descriptor. +See Table 5.1-1 Smart Card Device Descriptors in the CCID Specification [1]_. + +The value is a bitwise OR operation performed on the following values: + ++--------+--------------+ +| Value | Description | ++========+==============+ +| 0x0001 | Protocol T=0 | ++--------+--------------+ +| 0x0002 | Protocol T=1 | ++--------+--------------+ + +If no protocol is selected both T=0 and T=1 will be supported (`protocols` = 0x0003). + +nslots +~~~~~~ + +The `nslots` attribute writes to the bMaxSlotIndex field in the class descriptor. +See Table 5.1-1 Smart Card Device Descriptors in the CCID Specification [1]_. + +This is the index of the highest available slot on this device. All slots are consecutive starting at 00h. +i.e. 0Fh = 16 slots on this device numbered 00h to 0Fh. + +The default value is 0, which means one slot. + + +pinsupport +~~~~~~~~~~~~ + +This value indicates what PIN support features the CCID has. + +The `pinsupport` attribute writes to the dwPINSupport field in the class descriptor. +See Table 5.1-1 Smart Card Device Descriptors in the CCID Specification [1]_. + + +The value is a bitwise OR operation performed on the following values: + ++--------+----------------------------+ +| Value | Description | ++========+============================+ +| 0x00 | No PIN support | ++--------+----------------------------+ +| 0x01 | PIN Verification supported | ++--------+----------------------------+ +| 0x02 | PIN Modification supported | ++--------+----------------------------+ + +The default value is set to 0x00. + + +lcdlayout +~~~~~~~~~~ + +Number of lines and characters for the LCD display used to send messages for PIN entry. + +The `lcdLayout` attribute writes to the wLcdLayout field in the class descriptor. +See Table 5.1-1 Smart Card Device Descriptors in the CCID Specification [1]_. + + +The value is set as follows: + ++--------+------------------------------------+ +| Value | Description | ++========+====================================+ +| 0x0000 | No LCD | ++--------+------------------------------------+ +| 0xXXYY | XX: number of lines | +| | YY: number of characters per line. | ++--------+------------------------------------+ + +The default value is set to 0x0000. + + +Example +------- + +Here is an example on how to setup a CCID gadget with configfs :: + + #!/bin/sh + + CONFIGDIR=/sys/kernel/config + GADGET=$CONFIGDIR/usb_gadget/g0 + FUNCTION=$GADGET/functions/ccid.sc0 + + VID=YOUR_VENDOR_ID_HERE + PID=YOUR_PRODUCT_ID_HERE + UDC=YOUR_UDC_HERE + + #Mount filesystem + mount none -t configfs $CONFIGDIR + + #Populate ID:s + echo $VID > $GADGET/idVendor + echo $PID > $GADGET/idProduct + + #Create and configure the gadget + mkdir $FUNCTION + echo 0x000407B8 > $FUNCTION/features + echo 0x02 > $FUNCTION/protocols + + #Create our english strings + mkdir $GADGET/strings/0x409 + echo 556677 > $GADGET/strings/0x409/serialnumber + echo "Hungry Penguins" > $GADGET/strings/0x409/manufacturer + echo "Harpoon With SmartCard" > $GADGET/strings/0x409/product + + #Create configuration + mkdir $GADGET/configs/c.1 + mkdir $GADGET/configs/c.1/strings/0x409 + echo Config1 > $GADGET/configs/c.1/strings/0x409/configuration + + #Use `Config1` for our CCID gadget + ln -s $FUNCTION $GADGET/configs/c.1 + + #Execute + echo $UDC > $GADGET/UDC + + +References +========== + +.. [1] http://www.usb.org/developers/docs/devclass_docs/DWG_Smart-Card_CCID_Rev110.pdf +.. [2] include/uapi/linux/usb/ccid.h -- 2.16.2 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
