[Qemu-devel] [PATCH] Parallel Port Direction Fix

[Vijay Kumar <vijaykumar@bravegnu.org>]

The direction bit in the control register should not be directly
set using PPWCONTROL. The kernel gives the following debug message.

    parport0 (ppdev0): use data_reverse for this!

More over setting the data pins to forward mode does not work,
perhaps a bug in the Linux PP driver. The right way to do this is
to use PPDATADIR to set the direction. The patch checks if the
user is toggling the direction bit, and invokes PPDATADIR to
do the job.

Signed-off-by: Vijay Kumar B <vijaykumar@bravegnu.org>
---
diff -Naur qemu-orig/hw/parallel.c qemu-mod/hw/parallel.c
--- qemu-orig/hw/parallel.c	2008-06-10 16:58:10.000000000 +0530
+++ qemu-mod/hw/parallel.c	2008-06-10 16:47:23.000000000 +0530
@@ -129,6 +129,7 @@
 {
     ParallelState *s = opaque;
     uint8_t parm = val;
+    int dir;
 
     /* Sometimes programs do several writes for timing purposes on old
        HW. Take care not to waste time on writes that do nothing. */
@@ -154,6 +155,17 @@
         if (s->control == val)
             return;
         pdebug("wc%02x\n", val);
+
+        if ((val & PARA_CTR_DIR) != (s->control & PARA_CTR_DIR)) {
+            if (val & PARA_CTR_DIR) {
+                dir = 1;
+            } else {
+                dir = 0;
+            }
+            qemu_chr_ioctl(s->chr, CHR_IOCTL_PP_DATA_DIR, &dir);
+            parm &= ~PARA_CTR_DIR;
+        }
+
         qemu_chr_ioctl(s->chr, CHR_IOCTL_PP_WRITE_CONTROL, &parm);
         s->control = val;
         break;
diff -Naur qemu-orig/qemu-char.h qemu-mod/qemu-char.h
--- qemu-orig/qemu-char.h	2008-06-10 16:58:10.000000000 +0530
+++ qemu-mod/qemu-char.h	2008-06-10 16:39:24.000000000 +0530
@@ -27,6 +27,7 @@
 #define CHR_IOCTL_PP_EPP_READ         9
 #define CHR_IOCTL_PP_EPP_WRITE_ADDR  10
 #define CHR_IOCTL_PP_EPP_WRITE       11
+#define CHR_IOCTL_PP_DATA_DIR        12
 
 typedef void IOEventHandler(void *opaque, int event);
 
diff -Naur qemu-orig/vl.c qemu-mod/vl.c
--- qemu-orig/vl.c	2008-06-10 16:58:10.000000000 +0530
+++ qemu-mod/vl.c	2008-06-10 16:39:24.000000000 +0530
@@ -2525,6 +2525,10 @@
             return -ENOTSUP;
         *(uint8_t *)arg = b;
         break;
+    case CHR_IOCTL_PP_DATA_DIR:
+        if (ioctl(fd, PPDATADIR, (int *)arg) < 0)
+            return -ENOTSUP;
+        break;
     case CHR_IOCTL_PP_EPP_READ_ADDR:
 	if (pp_hw_mode(drv, IEEE1284_MODE_EPP|IEEE1284_ADDR)) {
 	    struct ParallelIOArg *parg = arg;