Wojtek Pilorz <wpilorz@bdk.pl> reported:

>I have just compiled cdrtools 1.11a38 on my system (RedHat Linux 6.2,
>Linux kernel 2.2.19+IDE patches), and cdrecord seems to always respond 
>with 'Resource temporarily unavailable. Cannot send SCSI cmd via ioctl';
>even -scanbus does not work;

Introducing important (even if small) changes short before a major release date
never is good.

It seems that it was a bad idea to trust Linus Torvalds when incorporating
a patch send by him.... he just does not know enough about constraints of
the Linux SCSI driver system :-(

Here is a patch that tries to work around the problems. Please test and report.
If it does not work for all of you, I will need to remove the patch from Linus
completely.

------- scsi-linux-sg.c -------
*** /tmp/da004wW	Thu Jan  1 01:00:00 1970
--- scsi-linux-sg.c	Sun Oct 20 14:15:08 2002
***************
*** 186,191 ****
--- 186,192 ----
  #ifdef	SG_IO
  LOCAL	int	sg_rwsend	__PR((SCSI *scgp));
  #endif
+ LOCAL	void	sg_clearnblock	__PR((int f));
  LOCAL	BOOL	sg_setup	__PR((SCSI *scgp, int f, int busno, int tgt, int tlun));
  LOCAL	void	sg_initdev	__PR((SCSI *scgp, int f));
  LOCAL	int	sg_mapbus	__PR((SCSI *scgp, int busno, int ino));
***************
*** 325,330 ****
--- 326,332 ----
  
  	for (i=0; i < 32; i++) {
  		js_snprintf(devname, sizeof(devname), "/dev/sg%d", i);
+ 					/* O_NONBLOCK is dangerous */
  		f = open(devname, O_RDWR | O_NONBLOCK);
  		if (f < 0) {
  			/*
***************
*** 341,346 ****
--- 343,349 ----
  				return (0);
  			}
  		} else {
+ 			sg_clearnblock(f);	/* Be very proper about this */
  			if (sg_setup(scgp, f, busno, tgt, tlun))
  				return (++nopen);
  			if (busno < 0 && tgt < 0 && tlun < 0)
***************
*** 352,357 ****
--- 355,361 ----
  		
  	if (nopen == 0) for (i=0; i <= 25; i++) {
  		js_snprintf(devname, sizeof(devname), "/dev/sg%c", i+'a');
+ 					/* O_NONBLOCK is dangerous */
  		f = open(devname, O_RDWR | O_NONBLOCK);
  		if (f < 0) {
  			/*
***************
*** 368,373 ****
--- 372,378 ----
  				return (0);
  			}
  		} else {
+ 			sg_clearnblock(f);	/* Be very proper about this */
  			if (sg_setup(scgp, f, busno, tgt, tlun))
  				return (++nopen);
  			if (busno < 0 && tgt < 0 && tlun < 0)
***************
*** 383,388 ****
--- 388,394 ----
  			js_fprintf((FILE *)scgp->errfile,
  			"Warning: Open by 'devname' is unintentional and not supported.\n");
  		}
+ 					/* O_NONBLOCK is dangerous */
  		f = open(device, O_RDWR | O_NONBLOCK);
  /*		if (f < 0 && errno == ENOENT)*/
  /*			goto openpg;*/
***************
*** 400,405 ****
--- 406,412 ----
  			return (0);
  		}
  
+ 		sg_clearnblock(f);		/* Be very proper about this */
  		if (!sg_mapdev(scgp, f, &busno, &tgt, &tlun, 0, 0)) {
  			close(f);
  			/*
***************
*** 476,481 ****
--- 483,507 ----
  	pg_close(scgp);
  #endif
  	return (0);
+ }
+ 
+ /*
+  * The Linux kernel becomes more and more unmaintainable.
+  * Every year, a new incompatible SCSI transport interface is introduced.
+  * Each of them has it's own contradictory constraints.
+  * While you cannot have O_NONBLOCK set during operation, at leat one
+  * of the drivers requires O_NONBLOCK to be set during open().
+  * This is used to clear O_NONBLOCK immediately after open() succeeded.
+  */
+ LOCAL void
+ sg_clearnblock(f)
+ 	int	f;
+ {
+ 	int	n;
+ 
+ 	n = fcntl(f, F_GETFL);
+ 	n &= ~O_NONBLOCK;
+ 	fcntl(f, F_SETFL, n);
  }
  
  LOCAL BOOL

Jörg

 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de		(uni)  If you don't have iso-8859-1
       schilling@fokus.gmd.de		(work) chars I am J"org Schilling
 URL:  http://www.fokus.gmd.de/usr/schilling   ftp://ftp.fokus.gmd.de/pub/unix
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