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>

1 files changed, 4 insertions, 3 deletions

diff --git a/hw/baum.c b/hw/baum.c
index 2aaf5ff..33a22a7 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;
 }