[ot] hw/opentitan: add a function to retrieve a CharDev by its id

Signed-off-by: Emmanuel Blot <eblot@rivosinc.com>

hw/opentitan/ot_common.c

@@ -27,6 +27,7 @@
 
 #include "qemu/osdep.h"
 #include "qom/object.h"
+#include "chardev/chardev-internal.h"
 #include "hw/opentitan/ot_common.h"
 
 typedef struct {
@@ -107,3 +108,37 @@ void ot_common_ignore_chr_status_lines(CharBackend *chr)
     tcsetattr(fioc->fd, TCSANOW, &tty);
 #endif
 }
+
+typedef struct {
+    Chardev *chr;
+    const char *label;
+} OtCommonChrMatch;
+
+static int ot_common_match_chardev(Object *child, void *opaque)
+{
+    OtCommonChrMatch *match = opaque;
+    Chardev *chr = CHARDEV(child);
+
+    if (strcmp(match->label, chr->label) != 0) {
+        return 0;
+    }
+
+    match->chr = chr;
+    return 1;
+}
+
+Chardev *ot_common_get_chardev_by_id(const char *chrid)
+{
+    OtCommonChrMatch match = {
+        .chr = NULL,
+        .label = chrid,
+    };
+
+    /* "chardev-internal.h" inclusion is required for get_chardevs_root() */
+    if (!object_child_foreach(get_chardevs_root(), &ot_common_match_chardev,
+                              &match)) {
+        return NULL;
+    }
+
+    return match.chr;
+}

include/hw/opentitan/ot_common.h

@@ -142,6 +142,19 @@ AddressSpace *ot_common_get_local_address_space(DeviceState *s);
 /* CharDev utilities */
 /* ------------------------------------------------------------------------ */
 
+/**
+ * Configure a (PTY) char backend to ignore status lines.
+ *
+ * @chr the character backend to configure.
+ */
 void ot_common_ignore_chr_status_lines(CharBackend *chr);
 
+/**
+ * Find a char device by its id, e.g. "-chardev type,id=<id>,...`"
+ *
+ * @chrid the id of the char device
+ * @return the char device if found, @c NULL otherwise.
+ */
+Chardev *ot_common_get_chardev_by_id(const char *chrid);
+
 #endif /* HW_OPENTITAN_OT_COMMON_H */