ccid-card-passthru, dev-smartcard-reader: add debug environment variables

Introduces a new utility function: parse_debug_env to avoid code
duplication.

This overrides whatever debug value is set on the corresponding devices
from the command line, and is meant to ease the usage with any
management stack. For libvirt you can set environment variables by
extending the dom namespace, i.e:

<domain type='kvm' id='3' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <qemu:commandline>
    <qemu:env name='QEMU_CCID_PASSTHRU_DEBUG' value='4'/>
    <qemu:env name='QEMU_CCID_DEBUG' value='4'/>
  </qemu:commandline>
</domain>

Signed-off-by: Alon Levy <alevy@redhat.com>
Reviewed-by: Marc-André Lureau <mlureau@redhat.com>

4 files changed, 31 insertions, 0 deletions

diff --git a/hw/usb/ccid-card-passthru.c b/hw/usb/ccid-card-passthru.c
index 16d51c9295..01c7e6f20d 100644
--- a/hw/usb/ccid-card-passthru.c
+++ b/hw/usb/ccid-card-passthru.c
@@ -350,6 +350,8 @@ static int passthru_initfn(CCIDCardState *base)
         error_report("missing chardev");
         return -1;
     }
+    card->debug = parse_debug_env("QEMU_CCID_PASSTHRU_DEBUG", D_VERBOSE,
+                                  card->debug);
     assert(sizeof(DEFAULT_ATR) <= MAX_ATR_SIZE);
     memcpy(card->atr, DEFAULT_ATR, sizeof(DEFAULT_ATR));
     card->atr_length = sizeof(DEFAULT_ATR);
diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c
index 98f3be1f0f..35f234e6ad 100644
--- a/hw/usb/dev-smartcard-reader.c
+++ b/hw/usb/dev-smartcard-reader.c
@@ -1260,6 +1260,7 @@ static int ccid_initfn(USBDevice *dev)
     s->bulk_out_pos = 0;
     ccid_reset_parameters(s);
     ccid_reset(s);
+    s->debug = parse_debug_env("QEMU_CCID_DEBUG", D_VERBOSE, s->debug);
     return 0;
 }
 
diff --git a/include/qemu-common.h b/include/qemu-common.h
index 3b1873e4ef..a39cdba27f 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -482,4 +482,9 @@ can_use_buffer_find_nonzero_offset(const void *buf, size_t len)
 }
 size_t buffer_find_nonzero_offset(const void *buf, size_t len);
 
+/*
+ * helper to parse debug environment variables
+ */
+int parse_debug_env(const char *name, int max, int initial);
+
 #endif
diff --git a/util/cutils.c b/util/cutils.c
index 5024253405..a1658197cf 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -482,3 +482,26 @@ int uleb128_decode_small(const uint8_t *in, uint32_t *n)
         return 2;
     }
 }
+
+/*
+ * helper to parse debug environment variables
+ */
+int parse_debug_env(const char *name, int max, int initial)
+{
+    char *debug_env = getenv(name);
+    char *inv = NULL;
+    int debug;
+
+    if (!debug_env) {
+        return initial;
+    }
+    debug = strtol(debug_env, &inv, 10);
+    if (inv == debug_env) {
+        return initial;
+    }
+    if (debug < 0 || debug > max) {
+        fprintf(stderr, "warning: %s not in [0, %d]", name, max);
+        return initial;
+    }
+    return debug;
+}