Re: [Libcdio-devel] Read Sub-channel changes

[Thomas Schmitt]

Hi,

Leon Merten Lohse wrote:
> Although it is allowed, it might give some drives a hiccup.

It's not about the drives but about the low-level drivers in the
operating systems. Those which act underneath SCSI passthrough
like Linux ioclt(SG_IO).
In my case i lost the connection to a USB connected DVD burner
when i requested more bytes than available. The request size is
also an announcement to the kernel and its drivers. Some of them
took offense.

I do not quite remember what was the problem with cdrecord ...
Possibly this one:
  https://lists.debian.org/cdwrite/2007/05/msg00042.html
Effects look more harmless than mine.
  "Input/output error. get performance: scsi sendcmd: no error"
(The pointer given to a FreeBSD problem is probably a red herring.
 Both problems look unrelated.)

I do not know from where Andy Polyakov (growisofs) got the idea or
why he deemed it necessary. But i remember that i first riddled why
he does it and then had the incident which made me smarter.


> Also the majority of the code in mmc.c in libcdio just uses one query.

That's a valid point on the one hand. But on the other hand the
double call is best practice and if it ever shall become part of
libcdio one has to start at some point. So why not now ?


Have a nice day :)

Thomas