21 Feb
2017
21 Feb
'17
10:38 p.m.
Diomidis Spinellis wrote:
On 21/02/2017 17:18, Joerg Schilling wrote:
This is an interesting point. However, controlling the C/A/T
phototypesetter 20 years before writable CD-ROM appeared, was also a
very complex task, yet it was accomplished through a simple device file.
Controlling a voice modem is also complex, time-critical, and requires
bidirectional communication. Again, voice modems were controlled through
a character device file.
How would you handle the different writing methods? Separate device
files or an ioctl on a generic device node?
(not arguing - genuinely curious about your theory)
Requiring
"pass through SCSI" for a CD burner violates the UNIX
philosophy that everything is a file (which implies that reading and
writing data be implemented, where possible, through the read and write
system calls rather than through special interfaces specific to a device
type).
You are incorrectly informed:
Writing CDs is a highly complex task. No known kernel is able to do that
internally.
So the only useful method is to use SCSI pass through.
One can envisage a CD-ROM device driver abstracting the commands
required for writing CD-ROMs into a text-based interface made available
though a character device. These precedents demonstrate that the SCSI
pass through was an unneeded architecture-violating shortcut.
Arguably, the same can also be claimed for the networking system calls.
Diomidis