From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753591AbeE3LfK (ORCPT ); Wed, 30 May 2018 07:35:10 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:40452 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753055AbeE3LfE (ORCPT ); Wed, 30 May 2018 07:35:04 -0400 X-Google-Smtp-Source: ADUXVKJY+qEPIkfynzr2V8Rs65Vk+eMMAZRAelvIvl2rINH/9yU7+kuBOLsfRlHgprRv25Oep6rFGA== Date: Wed, 30 May 2018 13:34:59 +0200 From: Marcus Folkesson To: Randy Dunlap Cc: Greg Kroah-Hartman , Jonathan Corbet , Felipe Balbi , davem@davemloft.net, Mauro Carvalho Chehab , Andrew Morton , Ruslan Bilovol , Thomas Gleixner , Kate Stewart , linux-usb@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/3] Documentation: usb: add documentation for USB CCID Gadget Device Message-ID: <20180530113459.GC2939@gmail.com> References: <20180529185021.13738-1-marcus.folkesson@gmail.com> <20180529185021.13738-2-marcus.folkesson@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Randy, On Tue, May 29, 2018 at 01:27:23PM -0700, Randy Dunlap wrote: > 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 > > --- > > > > 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 > > + > > +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. You are right, it is not clear. The devices are named as /dev/ccidg[0-4] and is per device. Writing/reading to the device is using BULK-IN/BULK-OUT, the /dev/ccidg* device is not bound to a particular endpoint. I will come up with something that make it more clear. Thank you! > > > + > > + > > +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 > > > thanks, > -- > ~Randy Best regards, Marcus Folkesson