On 05/29/2018 11:50 AM, Marcus Folkesson wrote: > 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> > --- > > Notes: > v3: > - correct the grammer (thanks Randy) > v2: > - add the missing changelog text > > 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..524fe9e6ac19 > --- /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 are 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. I think that it would be helpful to tell us what the naming of the /dev/ccidg* endpoints looks like. Also, how to distinguish the BULK-IN from the BULK-OUT endpoint. > + > + > +CCID Commands > +-------------- > + > +All CCID commands begins with a 10-byte 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 specify which slot 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 file descriptor is allowed to be open to the device at a time. Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> thanks, -- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
