diff --git a/docs/ddk/tracing.md b/docs/ddk/tracing.md
index 3836ac916c362c26e1d03fc8736af884bdc1dec6..1f02b248c302c2864e3641490391c7c45da78261 100644
--- a/docs/ddk/tracing.md
+++ b/docs/ddk/tracing.md
@@ -87,8 +87,11 @@ compile flag to enable it: `ENABLE_DRIVER_TRACING=true`,
it also requires an extra kernel command line flag to enable it:
`driver.tracing.enable=1`
-`ENABLE_DRIVER_TRACING=true` is now the default. To disable driver tracing,
-pass `ENABLE_DRIVER_TRACING=false` to make.
+`ENABLE_DRIVER_TRACING=true` is now the default. To disable compiling in
+driver tracing support, pass `ENABLE_DRIVER_TRACING=false` to make.
+
+`driver.tracing.enable=1` is also now the default. To disable partipation
+of drivers in Fuchsia tracing, boot the kernel with `driver.tracing.enable=0`.
Example:
@@ -103,13 +106,13 @@ $ fx build
Then boot. With QEMU:
```sh
-$ fx run -k -N -c driver.tracing.enable=1
+$ fx run -k -N
```
Or on h/w (augment with options specific to your h/w):
```sh
-$ fx serve -- -- driver.tracing.enable=1
+$ fx serve
```
These extra requirements will be removed once tracing support stabilizes.
diff --git a/docs/kernel_cmdline.md b/docs/kernel_cmdline.md
index ea5fd4c7963efea6b5ae22ba154a63c7fd92c718..beb673c17a97afe13bceacc4f3c7f413eaa47494 100644
--- a/docs/kernel_cmdline.md
+++ b/docs/kernel_cmdline.md
@@ -88,6 +88,17 @@ ZIRCON\_DRIVER\_BEGIN macro. It is not, for example, the name of the device,
which for some drivers is almost identical, except that the device may be
named "foo-bar" whereas the driver name must use underscores, e.g., "foo_bar".
+## driver.tracing.enable=\<bool>
+
+Enable or disable support for tracing drivers.
+When enabled drivers may participate in [Fuchsia tracing](ddk/tracing.md).
+
+Implementation-wise, what this option does is tell each devhost whether to
+register as "trace provider".
+
+The default is enabled. This options exists to provide a quick fallback should
+a problem arise.
+
## gfxconsole.early=\<bool>
This option (disabled by default) requests that the kernel start a graphics
diff --git a/system/core/devmgr/devhost/devhost.cpp b/system/core/devmgr/devhost/devhost.cpp
index 01463b7a86565f715055f13292faa015674447e8..a507c835d07cd03a0ba629e27c9e4b345e8daab6 100644
--- a/system/core/devmgr/devhost/devhost.cpp
+++ b/system/core/devmgr/devhost/devhost.cpp
@@ -45,6 +45,7 @@
#if ENABLE_DRIVER_TRACING
#include "tracing.h"
#endif
+#include "../shared/env.h"
#include "../shared/fidl_txn.h"
#include "../shared/log.h"
@@ -1182,8 +1183,7 @@ __EXPORT int device_host_main(int argc, char** argv) {
#if ENABLE_DRIVER_TRACING
{
- const char* enable = getenv("driver.tracing.enable");
- if (enable && strcmp(enable, "1") == 0) {
+ if (getenv_bool("driver.tracing.enable", true)) {
r = devhost_start_trace_provider();
if (r != ZX_OK) {
log(INFO, "devhost: error registering as trace provider: %d\n", r);
diff --git a/system/core/devmgr/devmgr/coordinator.cpp b/system/core/devmgr/devmgr/coordinator.cpp
index b41f7139077964e571afdeabf775ebb0d3b45dab..8b292c4ef74a5716a1d17d6b193c8ad2c6514847 100644
--- a/system/core/devmgr/devmgr/coordinator.cpp
+++ b/system/core/devmgr/devmgr/coordinator.cpp
@@ -36,6 +36,7 @@
#include <utility>
#include "devmgr.h"
+#include "../shared/env.h"
#include "../shared/fdio.h"
#include "../shared/fidl_txn.h"
#include "../shared/log.h"
diff --git a/system/core/devmgr/devmgr/drivers.cpp b/system/core/devmgr/devmgr/drivers.cpp
index 4b3109f9f7c42e9ce5f87909dc120f63344f16ee..556e4d949e368d174aa9dc46629a5a543e66591e 100644
--- a/system/core/devmgr/devmgr/drivers.cpp
+++ b/system/core/devmgr/devmgr/drivers.cpp
@@ -12,6 +12,7 @@
#include "coordinator.h"
#include "devmgr.h"
+#include "../shared/env.h"
#include "../shared/fdio.h"
#include "../shared/log.h"
diff --git a/system/core/devmgr/devmgr/main.cpp b/system/core/devmgr/devmgr/main.cpp
index ca43ea9b7e025ba9bfe81fe343d2120af026d59f..3ab06d20e3c6a3cec6ed65d80de22d68bbbf460f 100644
--- a/system/core/devmgr/devmgr/main.cpp
+++ b/system/core/devmgr/devmgr/main.cpp
@@ -40,6 +40,7 @@
#include <lib/zx/time.h>
#include <lib/zx/vmo.h>
+#include "../shared/env.h"
#include "../shared/fdio.h"
#include "coordinator.h"
#include "devmgr.h"
diff --git a/system/core/devmgr/fshost/fshost.h b/system/core/devmgr/fshost/fshost.h
index f9b62647219f7584ea213acd7fe1a67c8c93e443..0cd64ae089145d42b8c02d68859970e440e591d6 100644
--- a/system/core/devmgr/fshost/fshost.h
+++ b/system/core/devmgr/fshost/fshost.h
@@ -16,6 +16,7 @@
#include <zircon/thread_annotations.h>
#include <zircon/types.h>
+#include "../shared/env.h"
#include "../shared/fdio.h"
namespace devmgr {
diff --git a/system/core/devmgr/rules.mk b/system/core/devmgr/rules.mk
index 5909c8a62a98928d6ceb89cbe7a4bd61947d2ef9..ae1b9cac74cba6501fb0a056c98943b419152307 100644
--- a/system/core/devmgr/rules.mk
+++ b/system/core/devmgr/rules.mk
@@ -19,6 +19,7 @@ MODULE_SRCS += \
$(LOCAL_DIR)/devmgr/devfs.cpp \
$(LOCAL_DIR)/devmgr/drivers.cpp \
$(LOCAL_DIR)/devmgr/fidl.cpp \
+ $(LOCAL_DIR)/shared/env.cpp \
$(LOCAL_DIR)/shared/fdio.cpp \
# userboot supports loading via the dynamic linker, so libc (system/ulib/c)
@@ -80,6 +81,7 @@ MODULE_SRCS := \
$(LOCAL_DIR)/fshost/block-watcher.cpp \
$(LOCAL_DIR)/fshost/main.cpp \
$(LOCAL_DIR)/fshost/vfs-rpc.cpp \
+ $(LOCAL_DIR)/shared/env.cpp \
$(LOCAL_DIR)/shared/fdio.cpp \
MODULE_STATIC_LIBS := \
diff --git a/system/core/devmgr/shared/env.cpp b/system/core/devmgr/shared/env.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..a7f716f1121d477c4b53e09528660f5bc171fd0a
--- /dev/null
+++ b/system/core/devmgr/shared/env.cpp
@@ -0,0 +1,25 @@
+// Copyright 2018 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "env.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+namespace devmgr {
+
+bool getenv_bool(const char* key, bool default_value) {
+ const char* value = getenv(key);
+ if (value == nullptr) {
+ return default_value;
+ }
+ if ((strcmp(value, "0") == 0) ||
+ (strcmp(value, "false") == 0) ||
+ (strcmp(value, "off") == 0)) {
+ return false;
+ }
+ return true;
+}
+
+} // namespace devmgr
diff --git a/system/core/devmgr/shared/env.h b/system/core/devmgr/shared/env.h
new file mode 100644
index 0000000000000000000000000000000000000000..88f7b38567f14d1239bcf22cbe65def28bce702f
--- /dev/null
+++ b/system/core/devmgr/shared/env.h
@@ -0,0 +1,14 @@
+// Copyright 2018 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+namespace devmgr {
+
+// getenv_bool looks in the environment for |key|. If not found, it
+// returns |default_value|. If found, it returns false if the found
+// value matches "0", "off", or "false", otherwise it returns true.
+bool getenv_bool(const char* key, bool default_value);
+
+} // namespace devmgr
diff --git a/system/core/devmgr/shared/fdio.cpp b/system/core/devmgr/shared/fdio.cpp
index 94d1494011964b41a5d45e126f101670bc06e8f9..03cf73e54c01f7044215655686ac6eecebaa470a 100644
--- a/system/core/devmgr/shared/fdio.cpp
+++ b/system/core/devmgr/shared/fdio.cpp
@@ -174,17 +174,4 @@ zx_status_t devmgr_launch_cmdline(
return status;
}
-bool getenv_bool(const char* key, bool default_value) {
- const char* value = getenv(key);
- if (value == nullptr) {
- return default_value;
- }
- if ((strcmp(value, "0") == 0) ||
- (strcmp(value, "false") == 0) ||
- (strcmp(value, "off") == 0)) {
- return false;
- }
- return true;
-}
-
} // namespace
diff --git a/system/core/devmgr/shared/fdio.h b/system/core/devmgr/shared/fdio.h
index a6e062b904046786e041b3b8c231b643aab530dc..3d785ee956232e9fc7a477a666e7644b5c0fd6b2 100644
--- a/system/core/devmgr/shared/fdio.h
+++ b/system/core/devmgr/shared/fdio.h
@@ -51,11 +51,6 @@ zx_status_t devmgr_launch_cmdline(
const zx_handle_t* handles, const uint32_t* types, size_t hcount,
zx::process* proc_out, uint32_t flags);
-// getenv_bool looks in the environment for |key|. If not found, it
-// returns |default_value|. If found, it returns false if the found
-// value matches "0", "off", or "false", otherwise it returns true.
-bool getenv_bool(const char* key, bool default_value);
-
// The variable to set on the kernel command line to enable ld.so tracing
// of the processes we launch.
#define LDSO_TRACE_CMDLINE "ldso.trace"
diff --git a/system/ulib/driver/rules.mk b/system/ulib/driver/rules.mk
index 4e3355e53ccf1c436f123f2cc6a763246c8e9a20..f9e82d9043c181b2d84bd33bea51a42ae121d277 100644
--- a/system/ulib/driver/rules.mk
+++ b/system/ulib/driver/rules.mk
@@ -4,7 +4,8 @@
LOCAL_DIR := $(GET_LOCAL_DIR)
-DEVHOST_SRCS := system/core/devmgr/devhost
+LOCAL_DEVMGR_ROOT := system/core/devmgr
+LOCAL_DEVHOST_SRCS := $(LOCAL_DEVMGR_ROOT)/devhost
MODULE := $(LOCAL_DIR)
@@ -18,15 +19,16 @@ MODULE_SO_NAME := driver
MODULE_COMPILEFLAGS := -fvisibility=hidden
MODULE_SRCS := \
- $(DEVHOST_SRCS)/devhost.cpp \
- $(DEVHOST_SRCS)/api.cpp \
- $(DEVHOST_SRCS)/core.cpp \
- $(DEVHOST_SRCS)/rpc-server.cpp \
- $(DEVHOST_SRCS)/zx-device.cpp \
+ $(LOCAL_DEVHOST_SRCS)/devhost.cpp \
+ $(LOCAL_DEVHOST_SRCS)/api.cpp \
+ $(LOCAL_DEVHOST_SRCS)/core.cpp \
+ $(LOCAL_DEVHOST_SRCS)/rpc-server.cpp \
+ $(LOCAL_DEVHOST_SRCS)/zx-device.cpp \
+ $(LOCAL_DEVMGR_ROOT)/shared/env.cpp \
ifeq ($(call TOBOOL,$(ENABLE_DRIVER_TRACING)),true)
MODULE_SRCS += \
- $(DEVHOST_SRCS)/tracing.cpp
+ $(LOCAL_DEVHOST_SRCS)/tracing.cpp
MODULE_HEADER_DEPS := \
system/ulib/trace-provider
endif