[v2] USB:serial:pl2303:Add new PID to support PL2303HXN (TYPE_HXN)

[Johan Hovold <johan@kernel.org>]

On Mon, Apr 29, 2019 at 08:12:37PM +0800, Charles Yeh wrote:
> Prolific has developed a new USB to UART chip: PL2303HXN
> PL2303HXN : PL2303GC/PL2303GS/PL2303GT/PL2303GL/PL2303GE/PL2303GB
> The Vendor request used by the PL2303HXN (TYPE_HXN) is different from
> the existing PL2303 series (TYPE_HX & TYPE_01).
> Therefore, different Vendor requests are used to issue related commands.
> 
> 1. Added a new TYPE_HXN type in pl2303_type_data, and then executes
>    new Vendor request,new flow control and other related instructions
>    if TYPE_HXN is recognized.
> 
> 2. Because the new PL2303HXN only accept the new Vendor request,
>    the old Vendor request cannot be accepted (the error message
>    will be returned)
>    So first determine the TYPE_HX or TYPE_HXN through
>    PL2303_READ_TYPE_HX_STATUS in pl2303_startup.
> 
>   2.1 If the return message is "1", then the PL2303 is the existing
>       TYPE_HX/ TYPE_01 series.
>       The other settings in pl2303_startup are to continue execution.
>   2.2 If the return message is "not 1", then the PL2303 is the new
>       TYPE_HXN series.
>       The other settings in pl2303_startup are ignored.
>       (PL2303HXN will directly use the default value in the hardware,
>        no need to add additional settings through the software)
> 
> 3. In pl2303_open: Because TYPE_HXN is different from the instruction of reset
>    down/up stream used by TYPE_HX.
>    Therefore, we will also execute different instructions here.
> 
> 4. In pl2303_set_termios: The UART flow control instructions used by
>    TYPE_HXN/TYPE_HX/TYPE_01 are different.
>    Therefore, we will also execute different instructions here.
> 
> 5. In pl2303_vendor_read & pl2303_vendor_write, since TYPE_HXN is different
>    from the vendor request instruction used by TYPE_HX/TYPE_01,
>    it will also execute different instructions here.
> 
> Signed-off-by: Charles Yeh <charlesyeh522@gmail.com>
> ---

What changed in v2? You forgot to add a changelog here.

Looks like this one is not based on the current driver code (e.g. my
usb-next branch as we discussed), and also does not address some of the
issues raised so far (e.g. you're overwriting the entire flow control
register on updates).

I didn't have time to finish the prep work I promised to do, but don't
worry, I haven't forgotten.

Johan