Re: [PATCH] Revert "USB: serial: ch341: add new Product ID for CH341A"

[Dmytro Bagrii <dimich.dmb@gmail.com>]

On 08.02.22 12:34, Greg KH wrote:
> On Mon, Feb 07, 2022 at 02:08:23AM +0200, Dmytro Bagrii wrote:
>> This reverts commit 46ee4abb10a07bd8f8ce910ee6b4ae6a947d7f63.
> 
> You forgot to cc: the author of that commit, why?
> 
> Also forgot to cc: the maintainer of the driver/subsytem?

Sorry, forgot to add them. Also adding Johan Hovold, Frank A Kingswood 
and Frank Zago in the loop.

>> CH341A has three different modes of operation selectable either by
>> hardware pin connections or by external EEPROM configuration. Each
>> mode is represented by corresponding product ID:
>>
>> 0x5523: Asyncronous Serial Interface
>> 0x5584: Parallel Printer Interface
>> 0x5512: EPP/MEM Interface
> 
> That does not corrispond with what Jan-Niklas said in the original
> commit.

The page mentioned in the original commit is unavailable for me for some 
reason.

I refer to the chip manufacturer documentation from here: 
http://wch-ic.com/downloads/CH341DS1_PDF.html.

I have this kind of CH341A programmer: 
http://www.chinalctech.com/cpzx/Programmer/Serial_Module/266.html

When mode selection jumper is set to UART:

[52206.834474] usb 1-4.1: new full-speed USB device number 10 using xhci_hcd
[52206.925482] usb 1-4.1: New USB device found, idVendor=1a86, 
idProduct=5523, bcdDevice= 3.04
[52206.925494] usb 1-4.1: New USB device strings: Mfr=0, Product=0, 
SerialNumber=0
[52206.973701] usbcore: registered new interface driver ch341
[52206.973710] usbserial: USB Serial support registered for ch341-uart
[52206.973720] ch341 1-4.1:1.0: ch341-uart converter detected
[52206.974424] usb 1-4.1: ch341-uart converter now attached to ttyUSB0

ch341 creates /dev/ttyUSB0 and it works as a serial port, as expected.

When mode selection jumper is set to I2C/SPI (it uses EPP/MEM Interface):

[52413.942116] usb 1-4.1: new full-speed USB device number 11 using xhci_hcd
[52414.033085] usb 1-4.1: New USB device found, idVendor=1a86, 
idProduct=5512, bcdDevice= 3.04
[52414.033097] usb 1-4.1: New USB device strings: Mfr=0, Product=0, 
SerialNumber=0
[52414.040928] ch341 1-4.1:1.0: ch341-uart converter detected
[52414.041930] usb 1-4.1: ch341-uart converter now attached to ttyUSB0

ch341 creates /dev/ttyUSB0 but it doesn't work.

To use CH341A programmer as I2C/SPI converter either external module is 
required or userspace tools must be used. But they don't work until 
ch341 handles 1a86:5512.

If unbind device from ch341 module:

# echo 1-4.1:1.0 > /sys/bus/usb/drivers/ch341/unbind

I2C/SPI tools start to work correctly.

>> (See "5.3.Function configuration" in datasheet at wch-ic.com/downloads/CH341DS1_PDF.html)
>>
>> When CH341A is configured as EPP/MEM Interface it appears as 1a86:5512 and being mistakenly
>> handled by ch341 USB serial driver.
>>
>> It is possible to use CH341A in EPP/MEM mode only if ch341 module is blacklisted, but it must be
>> unblacklisted every time to use CH341A as a serial converter. Also obviously it is impossible
>> to use two CH341A boards in different modes simoultaneously.
> 
> Please wrap your lines at 72 columns.

Sure. Should i submit new patch verіon then?

> thanks,
> 
> greg k-h

-dmytro