[BRLTTY] [issue] HID braille device very slow under certain conditions

[Christian Schoepplein]

Hi Yannick,

On Tue, Jun 04, 2024 at 10:20:26AM +0200, Yannick PLASSIARD wrote:
>
>For a few weeks now, I have to use a Mac to do my job. I have two braille devices:
>- a Focus 5 USB device
>- A VarioUltra 40 USB-HID device
>
>Before that, I used these two devices on Windows and Linux without any particular issues, either on a real Linux system with Brltty 6.6, or in a Linux VM hosted by Windows with the same Brltty 6.6.
>
>On MacOS however I noticed something strange with my VarioUltra device: the transfer speed of the device (sending braille input / receiving braille dots to print) is very very slow. For example, if I type characters quickly, the device will freeze for several seconds and then the characters will be processed by BRLTTY, making it very inconfortable to use.
>
>About my current setup:
>- Running latest macOS Sonoma on an ARM64 (m2Pro) chip
>- Running latest VMWare Fusion software version to use a Linux ARM64 Debian virtual machine
>- Connect my braille device(s) to the VM and not to the Mac, so that BRLTTY can see and interact with them.
>
>
>My observations:
>- Using the Focus 40 5th generation connected to USB, everything works very well, nothing to complain about. I’m able to read and more importantly write very quickly  (typing at around 4 to 6 chars per second), and everything is responsive.
>- Using the VarioULTRA 40 connected to USB-HID to the same VM, things are very sluggish: typing at the same speed will result in the situation described above, i.e. slowness / freeze of the device until either a key is pressed, or a certain time.
>
>
>What I tried:
>1) With the Focus 40:
>- Works well everywhere: in a VM hosted by Windows/Mac, Linux host, and MacOS Host using the screen driver.
>2) With the VarioULTRA device: Works well on a Linux VM hosted by Windows and linux Host, become sluggish on a Linux VM hosted by MacOS.
>3) I tried to change hypervisors, and every software behaves the same, either with UTM or VMWare Fusion (UTM can use either QEMU backend for virtualisation, or Apple’s builtin virtualisation support).

I was playing around with a M1 Mac, Sonoma and Linux in a VM in the
past. I used UTM and Parallels as hypervisor and I am not using my
braille device as input device, just wanted it to use as a normal
braille output device. The braille device is a EL80C from Papenmeier.

My expierinces with Linux in a VM on the Mac were mixed:

- It was no problem to setup the VMs, no matter if I used UTM or Parallels. 
- I used VMware Fusion in the past on a Intell Mac but not on the M1
  machine. With VMware Fusion I worked for some months but I had also
  some problems that caused me to switch back to a normal Laptop with
  Linux or Windows and virtualize things there. Is the support of the
  Apple CPUs with VMware Fusion stable and fast meanwhile? I read that
  there are performance issues still with VMware Fusion, but if you are
  happy with the system speed I'd give it another try.
- Witzh UTM as hypervisor on my M1 machine I had the biggest problems
  with the USB connection of the braille device. That was the reason I
  gave up.
- With Paralles as hypervisor I had the best performance and the
  stablest system so far. But sometimes also the USB connection was
  disconnected and also I had very ofthen problems with the focus when
  switching between the VM and the host operating system.
- Attaching the braille device to the VMs worked in general, but very
  ofthen connection got lost, e.g. after the MacBook was in sleep mode.
  Do you have similar problems?
- Remapping the capslock key to use it as the screen reader key in the VM 
  was not easy.  For this problem I have no working solution so far. How 
  did you setup this? I was not able to find a working solution for UTM
  and Parallels, but in the past, wehn using VMware Fusion, I got it
  working somehow.
- Very ofthen the focus got lost when switching between the VM and the
  host operating system no matter what hypervisor I used.

Sorry to have no answer to your questions but maybe you do have ideas
how I could solve the problems I have, especialy the problem with the
remapping of the screen reader key. If I have a solution for this I
would again setup a Linux VM on my Mac and see how things are working
and maybe we can find solutions to your problems then.Also I'd be very
happy to write a guide for such a setup, because I know some other
people that have those problems with their Mac and virtulization too.

Ciao,

  Schoepp