[BRLTTY] Problem with brltty 3.9 on debian testing

[Michael Whapples]

On Tue, 2008-02-19 at 20:17 -0500, Dave Mielke wrote:
> [quoted lines by Nath on 2008/02/20 at 00:19 +0100]
> 
> >I have installed debian testing on my new Asus Eee pc and I encounter a
> >problem I never have had before : the braille display turns on sleep
> >mode every 4 or 5 seconds. when I press a key on the braille display or
> >on the laptop keyboard the braille display is up again but if I don't
> >press anything, 4 or 5 seconds after it is in sleep mode again.
> 
> You may be a victim of the automatic USB device suspension feature.

My thought when I saw this, power management of some sort. As a note
regarding this, I once tried powertop to determine how I might save
power, and I think USB device suspension came up and when I did that it
seemed to stop brltty properly initialising my display (an ALVA 544t).
The display seemed to get power (it beeped and presented the message
about waiting for connection), power seemed to be dropped and it started
again endlessly.
>  Brltty 
> currently disables this feature for Baum displays, but not for others. Perhaps 
> it should arbitrarily disable it for all displays. Let's figure out if this is 
> your problem:
> 
> Go (cd) to /sys/class/usb_device. In that directory you'll find a bunch of 
> devices with names like usbdev1.2. The first digit is the bus number and the 
> second digit is the device number.
> 
> The next thing to do is to figure out which of those usbdevx.y devices 
> corresponds to your display. Each of them is a directory whcih contains, among 
> other things, a subdirectory named device. Each of those device subdirectories 
> contains, among other things, a file named manufacturer. So, for example, to 
> check usbdev1.2, see what usbdev1.2/device/manufacturer says. Find the one 
> which names the manufacturer of your display.
> 
> When you find the usbdevx.y device which corresponds to your display, cd to 
> usbdevx.y/device/power. In there you'll find a file called autosuspend. Write 
> -1 to it, like this (assuming usbdev1.2):
> 
>    cd usbdev1.2/device/power
>    echo >autosuspend -1
> When powertop suggested doing this, I seem to remember a slightly different way of setting/unsetting this, and it was for the whole system. May be I remembered wrong, or may be both work but the way suggested by powertop is general and yours is specific to a device.

> Please let us know if this resolves your problem. If so, brltty will be updated 
> to handle this problem automatically.
> 
> One important thing to note is that the usbdevx.y name will change each time 
> you disconnect and reconnect your display so don't do that after you've written 
> to its autosuspend file else you'll have to do it again.
>