Make it easier to add more ptys to the pty(4) driver:

- Use unit2minor() and minor2unit() to generate minor numbers to support
  unit numbers higher than 255.
- Use simple string operations on the 'names' array rather than hard-coded
  constants and switch statements so that more ptys can be added by simply
  expanding the 'names' array.

MFC after:	1 week

1 files changed, 12 insertions, 19 deletions

diff --git a/sys/kern/tty_pty.c b/sys/kern/tty_pty.c
index 9079a64..01b7ae9 100644
--- a/sys/kern/tty_pty.c
+++ b/sys/kern/tty_pty.c
@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_tty.h"
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/libkern.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/sx.h>
@@ -127,9 +128,6 @@ static char *names = "pqrsPQRS";
  *
  * pts == /dev/tty[pqrsPQRS][0123456789abcdefghijklmnopqrstuv]
  * ptc == /dev/pty[pqrsPQRS][0123456789abcdefghijklmnopqrstuv]
- *
- * XXX: define and add mapping of upper minor bits to allow more
- *      than 256 ptys.
  */
 static struct cdev *
 ptyinit(struct cdev *devc, struct thread *td)
@@ -137,9 +135,10 @@ ptyinit(struct cdev *devc, struct thread *td)
 	struct ptsc *pt;
 	int n;
 
-	n = minor(devc);
-	/* For now we only map the lower 8 bits of the minor */
-	if (n & ~0xff)
+	n = minor2unit(minor(devc));
+
+	/* We only allow for up to 32 ptys per char in "names". */
+	if (n >= 32 * strlen(names))
 		return (NULL);
 
 	devc->si_flags &= ~SI_CHEAPCLONE;
@@ -760,32 +759,26 @@ static void
 pty_clone(void *arg, struct ucred *cr, char *name, int namelen,
     struct cdev **dev)
 {
+	char *cp;
 	int u;
 
 	if (*dev != NULL)
 		return;
 	if (bcmp(name, "pty", 3) != 0)
 		return;
-	if (name[5] != '\0')
+	if (name[5] != '\0' || name[3] == '\0')
 		return;
-	switch (name[3]) {
-	case 'p': u =   0; break;
-	case 'q': u =  32; break;
-	case 'r': u =  64; break;
-	case 's': u =  96; break;
-	case 'P': u = 128; break;
-	case 'Q': u = 160; break;
-	case 'R': u = 192; break;
-	case 'S': u = 224; break;
-	default: return;
-	}
+	cp = index(names, name[3]);
+	if (cp == NULL)
+		return;
+	u = (cp - names) * 32;
 	if (name[4] >= '0' && name[4] <= '9')
 		u += name[4] - '0';
 	else if (name[4] >= 'a' && name[4] <= 'v')
 		u += name[4] - 'a' + 10;
 	else
 		return;
-	*dev = make_dev_credf(MAKEDEV_REF, &ptc_cdevsw, u, cr,
+	*dev = make_dev_credf(MAKEDEV_REF, &ptc_cdevsw, unit2minor(u), cr,
 	    UID_ROOT, GID_WHEEL, 0666, "pty%c%r", names[u / 32], u % 32);
 	(*dev)->si_flags |= SI_CHEAPCLONE;
 	return;