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 16d51c929..01c7e6f20 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 98f3be1f0..35f234e6a 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 3b1873e4e..a39cdba27 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 502425340..a1658197c 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;
+}