Hi Randy, On Sun, May 27, 2018 at 04:36:24PM -0700, Randy Dunlap wrote: > Hi, > > I have a few documentation comments below... > > On 05/26/2018 02:19 PM, 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> > > --- > > 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*. > > are exposed > > > + > > +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 > > with a 10-byte header > (or maybe that's a locale difference) > > > +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 > > specify which slot is the receiver > > > +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. > > file descriptor > > > + > > +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. > > are > > > + > > +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]_. > > as defined > > > +The default value is 0x00000000. > > > [snip] > > HTH. > -- > ~Randy Thank you for your comments, I will take it with me for v3. Best regards Marcus Folkesson -- 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
