kern/52338: fd(4) floppy disk driver & non-blocking I/O

Yar Tikhiy yar at
Wed May 28 09:28:15 PDT 2003

As for panic in fdioctl(), I've been convinced upon second thought
that your approach should be preferred.  Indeed, for what sake may
the system happily return some fictitious media parameters before
the media has been detected?

I've considered just moving the media ioctl handlers to the blocking
part of fdioctl(), but this seemed to be a poor idea as long as the
media type was settable through ioctl(FD_STYPE), which gave non-null
fd->ft even in non-blocking mode.

The following patch does the same as your change to fdioctl() except
that fdioctl() will return EAGAIN if media type is unset in
non-blocking mode, as per fdc(4).  Does this look reasonable?

BTW, thank you for your valuable help on this topic.  I'd like to
express my deep respect to your comprehensive experience with the
system's internals.


--- fd.c.dist	Tue Apr  1 19:06:25 2003
+++ fd.c	Wed May 28 20:15:02 2003
@@ -2621,10 +2621,14 @@
 	switch (cmd) {
+		if (fd->ft == 0)
+			return ((fd->flags & FD_NONBLOCK) ? EAGAIN : ENXIO);
 		*(off_t *)addr = (128 << (fd->ft->secsize)) * fd->ft->size;
 		return (0);
+		if (fd->ft == 0)
+			return ((fd->flags & FD_NONBLOCK) ? EAGAIN : ENXIO);
 		*(u_int *)addr = 128 << (fd->ft->secsize);
 		return (0);

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