usb: serial: qcserial: add support for the Dell DW5821e module

On Tue, Jun 26, 2018 at 8:09 AM, Johan Hovold [off-list ref] wrote:

On Sat, Jun 23, 2018 at 11:24:08PM +0200, Aleksander Morgado wrote:

quoted

This module exposes two USB configurations: a QMI+AT capable setup on
USB config #1 and a MBIM capable setup on USB config #2.

By default the kernel will choose the MBIM capable configuration as
long as the cdc_mbim driver is available. This patch adds support for
the serial ports in the secondary configuration.

Could you please post the usb-devices output for this device?

Depending on another driver to select a specific configuration seems
fragile (and that behaviour is even configurable).

This would be when running on configuration #1:

T:  Bus=04 Lev=03 Prnt=04 Port=02 Cnt=01 Dev#=  7 Spd=5000 MxCh= 0
D:  Ver= 3.10 Cls=ef(misc ) Sub=02 Prot=01 MxPS= 9 #Cfgs=  2
P:  Vendor=413c ProdID=81d7 Rev=03.18
S:  Manufacturer=DELL
S:  Product=DW5821e Snapdragon X20 LTE
S:  SerialNumber=0123456789ABCDEF
C:  #Ifs= 5 Cfg#= 1 Atr=a0 MxPwr=896mA
I:  If#=0x0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=qcserial
I:  If#=0x1 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=ff Driver=qmi_wwan
I:  If#=0x2 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=qcserial
I:  If#=0x3 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=qcserial
I:  If#=0x4 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=(none)

This would be when running on configuration #2:

T:  Bus=04 Lev=03 Prnt=04 Port=02 Cnt=01 Dev#=  6 Spd=5000 MxCh= 0
D:  Ver= 3.10 Cls=ef(misc ) Sub=02 Prot=01 MxPS= 9 #Cfgs=  2
P:  Vendor=413c ProdID=81d7 Rev=03.18
S:  Manufacturer=DELL
S:  Product=DW5821e Snapdragon X20 LTE
S:  SerialNumber=0123456789ABCDEF
C:  #Ifs= 3 Cfg#= 2 Atr=a0 MxPwr=896mA
I:  If#=0x0 Alt= 0 #EPs= 1 Cls=02(commc) Sub=0e Prot=00 Driver=cdc_mbim
I:  If#=0x1 Alt= 1 #EPs= 2 Cls=0a(data ) Sub=00 Prot=02 Driver=cdc_mbim
I:  If#=0x2 Alt= 0 #EPs= 1 Cls=ff(vend.) Sub=ff Prot=ff Driver=qcserial