Strange graphics behavior when running Debian installer with USB-Serial adapter plugged in

[Shirobooon]

Hi, I recently installed Debian and noticed some peculiar behavior in the installer when I have my USB-Serial connector connected to the computer.

I have a Silicon Labs CP2102N based USB-Serial converter which is connected to my computer via USB.

Yesterday when I tried installing Debian, I first went with the graphical option, and to my surprise, instead of the GUI appearing, the screen turned like on the right side of the picture posted below.
It is like the standard text mode installer, but instead of being a regular framebuffer based one with support for non-latin characters, it looks reminiscent of the classic VGA font in old BIOS based systems.

I thought maybe my installation media was faulty, so I recreated one on a different USB drive, but I had the same result.

So next I tried the regular text mode installer, thinking the GUI based setup was broken somehow. However the screen on the right side of the picture was presented again, instead of the proper text installer.

I had never experienced this before in the multiple times I have installed Debian in the past. I remembered that I recently started using the USB-Serial converter, so I tested my luck and disconnected it and tried again, and to my surprise, everything worked as expected! The GUI installer properly showed, and the text mode installer worked properly too.


What was even more surprising, is that when I boot up the installer without the USB-Serial converter connected, into the proper installer (left side of picture), and then connect the USB-Serial converter, the screen goes black for a second, and then is redrawn to the VGA font style (right side of picture)


I can reliably reproduce this. Is this a bug, or is this documented and expected behavior? It was quite jarring to try the installer multiple times getting faulty graphics, only to discover that it was all caused simply by having a USB-Serial converter plugged in.

[lindi]

The installer supports serial console, allowing you to use it over the serial port.

[Shirobooon]

I'm assuming that means when it detects there is a serial port it automatically switches to that mode, and the screen mirrors what is being sent on serial?
As well as only supporting ASCII?

[Aki]

Hello,

[..]
What was even more surprising, is that when I boot up the installer without the USB-Serial converter connected, into the proper installer (left side of picture), and then connect the USB-Serial converter, the screen goes black for a second, and then is redrawn to the VGA font style (right side of picture)

I can reliably reproduce this. Is this a bug, or is this documented and expected behavior? It was quite jarring to try the installer multiple times getting faulty graphics, only to discover that it was all caused simply by having a USB-Serial converter plugged in.

I can not reproduce it in a virtual environment (with a virtual "usb-serial" device connected):

Code: Select all

<serial type="pty">
  <target type="usb-serial" port="0">
    <model name="usb-serial"/>
  </target>
  <address type="usb" bus="0" port="4"/>
</serial>

nor with the normal isa-serial:

Code: Select all

<serial type="pty">
  <target type="isa-serial" port="0">
    <model name="isa-serial"/>
  </target>
</serial>

I always obtain the same screen that appears on the left of your previous post.

Please note that there's something strange in the two screen dump you sent: the one on the right has an incomplete list of languages compared with the other on the left; are you really sure the two images were generated booting from the same ISO ?

[kalle123]

Have a lot of those adapters here. FTDI, CH340, PL2303, CP2102 and CP2104. Never seen a thing like that .....

[Shirobooon]

Hi Aki, this is indeed the same ISO. I uploaded a video showing me connect it in real time and the installer changing.

https://www.youtube.com/watch?v=tNwBI8jM9Is

[Aki]

Hi Aki, this is indeed the same ISO. I uploaded a video showing me connect it in real time and the installer changing.
https://www.youtube.com/watch?v=tNwBI8jM9Is

Can you report a link to the vendor/product specification and photos for the white USB device (with label "DC SD Adaptor V2") shown in the video ?

Isn't it a SD adapter for game consoles ?

Does it appear connected to the USB port of a game console and not to your computer with Debian ?

[kalle123]

Seems to be that one

https://de.aliexpress.com/item/1005004328522788.html

[Aki]

Seems to be that one
https://de.aliexpress.com/item/1005004328522788.html

Yes, I think so, too. Therefore, the OP is trying to plug a USB connector (from the black cable) in the SD port (!?!?) of an SD adapter connected to Dream Cast console. Well, perhaps the OP is kidding ....

[darcagn]

Therefore, the OP is trying to plug a USB connector (from the black cable) in the SD port (!?!?) of an SD adapter connected to Dream Cast console. Well, perhaps the OP is kidding ....

A user reports a bug with video footage and gets accusations of dishonesty?

I sold this adapter to Shirobooon. It's a custom PCB with a Silicon Labs CP2102N but it's a standard implementation. The USB end plugs into the computer and the serial end plugs into the Dreamcast.

Developers want to upload binaries to Dreamcast consoles via the Dreamcast's proprietary serial connector. The AliExpress vendor making SD card adapters is the only affordable source of these proprietary connectors, and they will not sell us connectors alone without a very large volume order which is far too unrealistic for our use case.

So I create serial link modules for Dreamcast developers by purchasing AliExpress SD adapters in bulk, to desolder and harvest their connectors. The CP2102N PCB is designed to be a drop-in replacement for the SD card PCB, that way, I can re-use the plastic housing instead of discarding it as waste. Conveniently, an SD slot opening is wide enough for a USB-C connector to pass through. The label "DC SD Adapter" does not affect the functionality, hope this helps.

[kalle123]

A user reports a bug with video footage and gets accusations of dishonesty?

Harsh words. We can only interpret, what we read and see here and that is quite confusing ....

[Aki]

Hello @darcagn,

Detailed information are usually required to address reports by users. So far, the OP was unable to report a reference to the manufacturer or an user manual apart from a video of the "object" without any detailed specification. The video itself was not showing the internals of the "object".

This topic does not seem to me to be very useful for further investigation as a Debian issue, even in light of the additional information you have provided.

Have a nice day.