Hi, the wodim device scan bug vanished and re-appeared with the Debian versions although /dev/scd* did not re-appear. So there must be some other influence.
I think i can prove from the source code that on kernels with minor revision number below 6 wodim enumerates /dev/sg*, whereas on kernels with minor revision number of 6 or larger it tries to enumerate /dev/scd*. /dev/sg* exist for any device under control of the SCSI driver. /dev/scd* have become out of fashion. (One can work around the bug by manually creating links from /dev/scd* to /dev/sr*.) So with kernel 3.2 of Wheezy the bug vanished and with 3.16 of Jessie it re-appeared. Early 4.X will not show the bug, but beginning with 4.6 it will be back again. So Stretch with kernel 4.9 will have it. Source study: https://sources.debian.net/src/cdrkit/9:1.1.11-3/libusal/scsi-linux-sg.c/#L509 /* scan and maybe keep one open, sg_setup decides */ #define HDX 0 #define SCD 1 #define SG 2 ... for(h=HDX; h <= (fake_atabus ? HDX : SG) ; h++) { ... switch(h) { case(HDX): { pattern="/dev/hd%c"; ... case(SCD): { if(!check_linux_26()) continue; pattern="/dev/scd%d"; ... case(SG): { if(check_linux_26()) continue; ... pattern="/dev/sg%d"; ... So it looks for /dev/hd* (drives under old IDE driver) in any case. If "check_linux_26()" is true, then it looks for /dev/scd*, which are missing because out of fashion. If "check_linux_26()" is false, then it looks for /dev/sg*, which exist. Beginning with Linux 2.5.X it became possible to use /dev/sr* for ioctl(SG_IO), which does the SCSI command transactions for wodim. So obviously the test shall distinguish kernel 2.6 or younger from kernel 2.5 or older. But at https://sources.debian.net/src/cdrkit/9:1.1.11-3/libusal/scsi-linux-sg.c/#L251 there seems to be missing the check for the major kernel version: BOOL check_linux_26() { int gen, tmp; struct utsname buf; return ( 0==uname( &buf ) && sscanf(buf.release, "%d.%d", &gen, &tmp)>1 && tmp>=6); } I tested this code on my Jessie. tmp has the value 16 and thus the function returns 1. So my wodim looks for /dev/scd*. If there is maintainer interest, then i would propose two code changes: ------------------------------------------------------------------------- In libusal/scsi-linux-sg.c, check_linux_26(), line 254: - return ( 0==uname( &buf ) && sscanf(buf.release, "%d.%d", &gen, &tmp)>1 && tmp>=6); + return ( 0==uname( &buf ) && sscanf(buf.release, "%d.%d", &gen, &tmp)>1 && (gen>2 || tmp>=6)); This will not change the function result in Jessie and Stretch but maybe in a future release with kernel 5.X. ------------------------------------------------------------------------- In libusal/scsi-linux-sg.c, usalo_open(), line 532: - pattern="/dev/scd%d"; + pattern="/dev/sr%d"; This will fix the enumeration bug on all kernels not older than 2.6. On older kernels /dev/sg* is still the right path to use. ------------------------------------------------------------------------- Have a nice day :) Thomas
