qemu-char: Print strerror message on failure

The only way for chardev drivers to communicate an error was to return a NULL
pointer, which resulted in an error message that said _that_ something went
wrong, but not _why_.

This patch changes the interface to return 0/-errno and updates
qemu_chr_open_opts to use strerror to display a more helpful error message.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

3 files changed, 8 insertions, 6 deletions

diff --git a/hw/baum.c b/hw/baum.c
index 2aaf5ffe9d..33a22a73d9 100644
--- a/hw/baum.c
+++ b/hw/baum.c
@@ -576,7 +576,7 @@ static void baum_close(struct CharDriverState *chr)
     qemu_free(baum);
 }
 
-CharDriverState *chr_baum_init(QemuOpts *opts)
+int chr_baum_init(QemuOpts *opts, CharDriverState **_chr)
 {
     BaumDriverState *baum;
     CharDriverState *chr;
@@ -629,7 +629,8 @@ CharDriverState *chr_baum_init(QemuOpts *opts)
 
     qemu_chr_generic_open(chr);
 
-    return chr;
+    *_chr = chr;
+    return 0;
 
 fail:
     qemu_free_timer(baum->cellCount_timer);
@@ -638,5 +639,5 @@ fail_handle:
     qemu_free(handle);
     qemu_free(chr);
     qemu_free(baum);
-    return NULL;
+    return -EIO;
 }
diff --git a/hw/msmouse.c b/hw/msmouse.c
index 05f893ca93..67c6cd43e0 100644
--- a/hw/msmouse.c
+++ b/hw/msmouse.c
@@ -64,7 +64,7 @@ static void msmouse_chr_close (struct CharDriverState *chr)
     qemu_free (chr);
 }
 
-CharDriverState *qemu_chr_open_msmouse(QemuOpts *opts)
+int qemu_chr_open_msmouse(QemuOpts *opts, CharDriverState **_chr)
 {
     CharDriverState *chr;
 
@@ -74,5 +74,6 @@ CharDriverState *qemu_chr_open_msmouse(QemuOpts *opts)
 
     qemu_add_mouse_event_handler(msmouse_event, chr, 0, "QEMU Microsoft Mouse");
 
-    return chr;
+    *_chr = chr;
+    return 0;
 }
diff --git a/hw/msmouse.h b/hw/msmouse.h
index 456cb21424..8b853b35bf 100644
--- a/hw/msmouse.h
+++ b/hw/msmouse.h
@@ -1,2 +1,2 @@
 /* msmouse.c */
-CharDriverState *qemu_chr_open_msmouse(QemuOpts *opts);
+int qemu_chr_open_msmouse(QemuOpts *opts, CharDriverState **_chr);