Hi Andrzej, Thank you for reviewing. On Mon, May 28, 2018 at 11:12:27AM +0200, Andrzej Pietrasiewicz wrote: > W dniu 28.05.2018 o 10:38, Marcus Folkesson pisze: > > Hi Andrzej, > > > > On Mon, May 28, 2018 at 09:04:51AM +0200, Andrzej Pietrasiewicz wrote: > >> Mi Marcus, > >> > >> W dniu 26.05.2018 o 23:19, Marcus Folkesson pisze: > >>> Chip Card Interface Device (CCID) protocol is a USB protocol that > >>> allows a smartcard device to be connected to a computer via a card > >>> reader using a standard USB interface, without the need for each manufacturer > >>> of smartcards to provide its own reader or protocol. > >>> > >>> This gadget driver makes Linux show up as a CCID device to the host and let a > >>> userspace daemon act as the smartcard. > >>> > >>> This is useful when the Linux gadget itself should act as a cryptographic > >>> device or forward APDUs to an embedded smartcard device. > >>> > >>> Signed-off-by: Marcus Folkesson <marcus.folkesson@xxxxxxxxx> > >>> --- > >> > >>> > >>> +config USB_CONFIGFS_CCID > >>> + bool "Chip Card Interface Device (CCID)" > >>> + depends on USB_CONFIGFS > >>> + select USB_F_CCID > >>> + help > >>> + The CCID function driver provides generic emulation of a > >>> + Chip Card Interface Device (CCID). > >>> + > >>> + You will need a user space server talking to /dev/ccidg*, > >>> + since the kernel itself does not implement CCID/TPDU/APDU > >>> + protocol. > >> > >> Your function needs a userspace daemon to work. > >> It seems you want to use FunctionFS for such a purpose > >> instead of creating a new function. > >> > >> Andrzej > > > >>> + since the kernel itself does not implement CCID/TPDU/APDU > > Oops, the driver does handle CCID. > > Which parts of code do this handling? My bad, I was thinking about the USB descriptors and endpoints setup. That is of cause not part of the CCID protocol. > > Is there any kind of state machine usual for protocols? > If the protocol is stateless then isn't it just a data format then? The protocol is stateless. > > Which part of this handling must be done in kernel and why? > > Does the said handling do anything other than forwarding the > traffic between USB and a character device? No, it forward the CCID messages to the character device to be handled by the application. > > What is the character device used for? I know: read, write and poll. > But why? To do what? It is used for the application to fetch, interpret and then perform actions depending on commands. > > > > > Well, yes, It needs an application that perform the "smartcard operations", such as > > generate keys or sign data, as this depends on how it should be used. > > > > The actual smartcard operations could for example be in software, > > use a crypto engine in SoC or external HSM (Hardware Security Module). > > > > Without the application, the gadget shows up as a smart card reader > > with an unconnected smartcard. > > > > Does showing up as anything require anything other than merely > providing USB descriptors? I guess. > > Andrzej Thank you, Marcus -- 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
