k3b: incorrect list of dvd writing speeds; Was: kern/106432: Record of disks (DVD-R) through the k3b program leads to lag of system

[Andriy Gapon]

Looks like maybe I was a little bit too hasty and there is a better
explanation and fix. Please see:
https://bugs.kde.org/show_bug.cgi?id=139985

on 12/01/2007 20:00 Andriy Gapon said the following:
> Guys,
> 
> FYI.
> 
> -------- Original Message --------
> Subject: Re: kern/106432: Record of disks (DVD-R) through the k3b
> program leads to lag of system
> Date: Fri, 12 Jan 2007 19:57:06 +0200
> From: Andriy Gapon <avg at icyb.net.ua>
> To: bug-followup at FreeBSD.org,  andrew at dobrohot.org,  h.eichmann at gmx.de
> 
> 
> I would like to followup on the portion of this PR that says that k3b
> shows incorrect speed list in its "Speed" drop-down for DVD media.
> 
> I have this problem as well and I think that I found a reason. The
> following lines from k3b debug output raised my suspicion:
> 
> k3b: (K3bDevice::openDevice) open device /dev/pass0 succeeded.
> k3b: (K3bDevice::ScsiCommand) transport command ac, length: 12
> k3b: (K3bDevice::openDevice) open device /dev/pass0 succeeded.
> k3b: (K3bDevice::ScsiCommand) transport command ac, length: 10
> k3b: (K3bDevice::Device) /dev/cd0:  Number of supported write speeds via
> GET PERFORMANCE: 7
> k3b: (K3bDevice::Device) /dev/cd0 : 13854 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 Invalid DVD speed: 0 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 Invalid DVD speed: 0 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 Invalid DVD speed: 0 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 Invalid DVD speed: 0 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 Invalid DVD speed: 0 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 Invalid DVD speed: 0 KB/s
> 
> It seems that the second 0xAC (GET PERFORMANCE) command was sent as
> 10-byte command instead of correct 12-byte command. I've checked the
> sources of k3b and dvd+rw-mediainfo and they both send two 0xAC commands
> , first one is to query number of writing profiles and the second one is
> to actually get them. Only dvd+rw-mediainfo does it correctly and k3b
> does it incorrectly.
> 
> The problem is in libk3bdevice/k3bdevice_mmc.cpp file, method
> K3bDevice::Device::getPerformance(): the code assumes that some bytes in
> cmd[] will survive the first execution and so they do not need to be set
> again. This might be an incorrect assumption. So I changed the
> corresponding lines so that they look like follows:
> [[[[]]]]
>     int numDesc = (dataLen-8)/16;
> 
>     cmd[0] = MMC_GET_PERFORMANCE;
>     cmd[1] = dataType;
>     cmd[2] = lba >> 24;
>     cmd[3] = lba >> 16;
>     cmd[4] = lba >> 8;
>     cmd[5] = lba;
>     cmd[8] = numDesc>>8;
>     cmd[9] = numDesc;
>     cmd[10] = type;
>     cmd[11] = 0;     // Necessary to set the proper command length
> [[[[]]]]
> 
> Now everything is correct:
> k3b: (K3bDevice::openDevice) open device /dev/pass0 succeeded.
> k3b: (K3bDevice::ScsiCommand) transport command ac, length: 12
> k3b: (K3bDevice::openDevice) open device /dev/pass0 succeeded.
> k3b: (K3bDevice::ScsiCommand) transport command ac, length: 12
> k3b: (K3bDevice::Device) /dev/cd0:  Number of supported write speeds via
> GET PERFORMANCE: 7
> k3b: (K3bDevice::Device) /dev/cd0 : 22161 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 : 22160 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 : 16621 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 : 16620 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 : 11081 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 : 11080 KB/s
> k3b: (K3bDevice::Device) /dev/cd0 : 5540 KB/s
> 
> And I see the correct list in GUI drop-down too.
> Before that I had to always set DVD writing speed to "Ignore", so that
> k3b wouldn't try to force some unnatural speed on my DVD drive.
> 
> 


-- 
Andriy Gapon