From 222455ef814935b1ecc6c9a75acbc0e97e31d8a7 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Mon, 8 Mar 2021 08:32:40 +0100
Subject: libqos/qgraph: format qgraph comments for sphinx documentation

Change documentation style and fix minor typos in tests/qtest/libqos/qgraph.h
to automatically generate sphinx documentation in docs/devel/qgraph.rst

The mechanism explanation that once was in qgraph.h is now moved to qgraph.rst

There is no functional change intended.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210308073240.6363-1-eesposit@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 docs/devel/index.rst  |   1 +
 docs/devel/qgraph.rst | 261 ++++++++++++++++++++++++++++++++++++++++++++++++++
 docs/devel/qtest.rst  |   8 ++
 3 files changed, 270 insertions(+)
 create mode 100644 docs/devel/qgraph.rst

(limited to 'docs/devel')

diff --git a/docs/devel/index.rst b/docs/devel/index.rst
index ae664da00c..7c424ea6d7 100644
--- a/docs/devel/index.rst
+++ b/docs/devel/index.rst
@@ -12,6 +12,7 @@ Contents:
 
 .. toctree::
    :maxdepth: 2
+   :includehidden:
 
    build-system
    style
diff --git a/docs/devel/qgraph.rst b/docs/devel/qgraph.rst
new file mode 100644
index 0000000000..62a45cbcbf
--- /dev/null
+++ b/docs/devel/qgraph.rst
@@ -0,0 +1,261 @@
+.. _qgraph:
+
+========================================
+Qtest Driver Framework
+========================================
+
+This Qgraph API provides all basic functions to create a graph
+and instantiate nodes representing machines, drivers and tests
+representing their relations with ``CONSUMES``, ``PRODUCES``, and
+``CONTAINS`` edges.
+
+The idea is to have a framework where each test asks for a specific
+driver, and the framework takes care of allocating the proper devices
+required and passing the correct command line arguments to QEMU.
+
+Nodes
+^^^^^^
+
+A node can be of four types:
+
+- **QNODE_MACHINE**:   for example ``arm/raspi2``
+- **QNODE_DRIVER**:    for example ``generic-sdhci``
+- **QNODE_INTERFACE**: for example ``sdhci`` (interface for all ``-sdhci``
+  drivers).
+  An interface is not explicitly created, it will be automatically
+  instantiated when a node consumes or produces it.
+- **QNODE_TEST**:      for example ``sdhci-test``, consumes an interface and
+  tests the functions provided.
+
+Notes for the nodes:
+
+- QNODE_MACHINE: each machine struct must have a ``QGuestAllocator`` and
+  implement ``get_driver()`` to return the allocator mapped to the interface
+  "memory". The function can also return ``NULL`` if the allocator
+  is not set.
+- QNODE_DRIVER:  driver names must be unique, and machines and nodes
+  planned to be "consumed" by other nodes must match QEMU
+  drivers name, otherwise they won't be discovered
+
+Edges
+^^^^^^
+
+An edge relation between two nodes (drivers or machines) `X` and `Y` can be:
+
+- ``X CONSUMES Y``: `Y` can be plugged into `X`
+- ``X PRODUCES Y``: `X` provides the interface `Y`
+- ``X CONTAINS Y``: `Y` is part of `X` component
+
+Execution steps
+^^^^^^^^^^^^^^^
+
+The basic framework steps are the following:
+
+- All nodes and edges are created in their respective
+  machine/driver/test files
+- The framework starts QEMU and asks for a list of available devices
+  and machines (note that only machines and "consumed" nodes are mapped
+  1:1 with QEMU devices)
+- The framework walks the graph starting from the available machines and
+  performs a Depth First Search for tests
+- Once a test is found, the path is walked again and all drivers are
+  allocated accordingly and the final interface is passed to the test
+- The test is executed
+- Unused objects are cleaned and the path discovery is continued
+
+Depending on the QEMU binary used, only some drivers/machines will be
+available and only test that are reached by them will be executed.
+
+Creating a new driver and its interface
+"""""""""""""""""""""""""""""""""""""""""
+
+.. code::
+
+    #include "qgraph.h"
+
+    struct My_driver {
+        QOSGraphObject obj;
+        Node_produced prod;
+        Node_contained cont;
+    }
+
+    static void my_destructor(QOSGraphObject *obj)
+    {
+        g_free(obj);
+    }
+
+    static void *my_get_driver(void *object, const char *interface) {
+        My_driver *dev = object;
+        if (!g_strcmp0(interface, "my_interface")) {
+            return &dev->prod;
+        }
+        abort();
+    }
+
+    static void *my_get_device(void *object, const char *device) {
+        My_driver *dev = object;
+        if (!g_strcmp0(device, "my_driver_contained")) {
+            return &dev->cont;
+        }
+        abort();
+    }
+
+    static void *my_driver_constructor(void *node_consumed,
+                                        QOSGraphObject *alloc)
+    {
+        My_driver dev = g_new(My_driver, 1);
+
+        // get the node pointed by the produce edge
+        dev->obj.get_driver = my_get_driver;
+
+        // get the node pointed by the contains
+        dev->obj.get_device = my_get_device;
+
+        // free the object
+        dev->obj.destructor = my_destructor;
+
+        do_something_with_node_consumed(node_consumed);
+
+        // set all fields of contained device
+        init_contained_device(&dev->cont);
+        return &dev->obj;
+    }
+
+    static void register_my_driver(void)
+    {
+        qos_node_create_driver("my_driver", my_driver_constructor);
+
+        // contained drivers don't need a constructor,
+        // they will be init by the parent.
+        qos_node_create_driver("my_driver_contained", NULL);
+
+        // For the sake of this example, assume machine x86_64/pc
+        // contains "other_node".
+        // This relation, along with the machine and "other_node"
+        // creation, should be defined in the x86_64_pc-machine.c file.
+        // "my_driver" will then consume "other_node"
+        qos_node_contains("my_driver", "my_driver_contained");
+        qos_node_produces("my_driver", "my_interface");
+        qos_node_consumes("my_driver", "other_node");
+    }
+
+In the above example, all possible types of relations are created:
+node "my_driver" consumes, contains and produces other nodes.
+More specifically::
+
+  x86_64/pc -->contains--> other_node <--consumes-- my_driver
+                                                        |
+                       my_driver_contained <--contains--+
+                                                        |
+                              my_interface <--produces--+
+
+or inverting the consumes edge in consumed_by::
+
+  x86_64/pc -->contains--> other_node --consumed_by--> my_driver
+                                                            |
+                           my_driver_contained <--contains--+
+                                                            |
+                                  my_interface <--produces--+
+
+Creating new test
+"""""""""""""""""
+
+.. code::
+
+    #include "qgraph.h"
+
+    static void my_test_function(void *obj, void *data)
+    {
+        Node_produced *interface_to_test = obj;
+        // test interface_to_test
+    }
+
+    static void register_my_test(void)
+    {
+        qos_add_test("my_interface", "my_test", my_test_function);
+    }
+
+    libqos_init(register_my_test);
+
+Here a new test is created, consuming "my_interface" node
+and creating a valid path from a machine to a test.
+Final graph will be like this::
+
+  x86_64/pc --contains--> other_node <--consumes-- my_driver
+                                                         |
+                        my_driver_contained <--contains--+
+                                                         |
+         my_test --consumes--> my_interface <--produces--+
+
+or inverting the consumes edge in consumed_by::
+
+  x86_64/pc --contains--> other_node --consumed_by--> my_driver
+                                                            |
+                           my_driver_contained <--contains--+
+                                                            |
+         my_test <--consumed_by-- my_interface <--produces--+
+
+Assuming there the binary is
+``QTEST_QEMU_BINARY=./qemu-system-x86_64``
+a valid test path will be:
+``/x86_64/pc/other_node/my_driver/my_interface/my_test``.
+
+Additional examples are also in ``test-qgraph.c``
+
+Command line:
+""""""""""""""
+
+Command line is built by using node names and optional arguments
+passed by the user when building the edges.
+
+There are three types of command line arguments:
+
+- ``in node``      : created from the node name. For example, machines will
+  have ``-M <machine>`` to its command line, while devices
+  ``-device <device>``. It is automatically done by the framework.
+- ``after node``   : added as additional argument to the node name.
+  This argument is added optionally when creating edges,
+  by setting the parameter @after_cmd_line and
+  @extra_edge_opts in #QOSGraphEdgeOptions.
+  The framework automatically adds
+  a comma before @extra_edge_opts,
+  because it is going to add attributes
+  after the destination node pointed by
+  the edge containing these options, and automatically
+  adds a space before @after_cmd_line, because it
+  adds an additional device, not an attribute.
+- ``before node``  : added as additional argument to the node name.
+  This argument is added optionally when creating edges,
+  by setting the parameter @before_cmd_line in
+  #QOSGraphEdgeOptions. This attribute
+  is going to add attributes before the destination node
+  pointed by the edge containing these options. It is
+  helpful to commands that are not node-representable,
+  such as ``-fdsev`` or ``-netdev``.
+
+While adding command line in edges is always used, not all nodes names are
+used in every path walk: this is because the contained or produced ones
+are already added by QEMU, so only nodes that "consumes" will be used to
+build the command line. Also, nodes that will have ``{ "abstract" : true }``
+as QMP attribute will loose their command line, since they are not proper
+devices to be added in QEMU.
+
+Example::
+
+    QOSGraphEdgeOptions opts = {
+        .arg = NULL,
+        .size_arg = 0,
+        .after_cmd_line = "-device other",
+        .before_cmd_line = "-netdev something",
+        .extra_edge_opts = "addr=04.0",
+    };
+    QOSGraphNodeS *node = qos_node_create_driver("my_node", constructor);
+    qos_node_consumes_args("my_node", "interface", &opts);
+
+Will produce the following command line:
+``-netdev something -device my_node,addr=04.0 -device other``
+
+Qgraph API reference
+^^^^^^^^^^^^^^^^^^^^
+
+.. kernel-doc:: tests/qtest/libqos/qgraph.h
diff --git a/docs/devel/qtest.rst b/docs/devel/qtest.rst
index 97c5a75626..c3dceb6c8a 100644
--- a/docs/devel/qtest.rst
+++ b/docs/devel/qtest.rst
@@ -2,6 +2,11 @@
 QTest Device Emulation Testing Framework
 ========================================
 
+.. toctree::
+   :hidden:
+
+   qgraph
+
 QTest is a device emulation testing framework.  It can be very useful to test
 device models; it could also control certain aspects of QEMU (such as virtual
 clock stepping), with a special purpose "qtest" protocol.  Refer to
@@ -24,6 +29,9 @@ On top of libqtest, a higher level library, ``libqos``, was created to
 encapsulate common tasks of device drivers, such as memory management and
 communicating with system buses or devices. Many virtual device tests use
 libqos instead of directly calling into libqtest.
+Libqos also offers the Qgraph API to increase each test coverage and
+automate QEMU command line arguments and devices setup.
+Refer to :ref:`qgraph` for Qgraph explanation and API.
 
 Steps to add a new QTest case are:
 
-- 
cgit v1.2.3


From afdbd38223cc1aafdac5cc29074e8bd5508a80df Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Mon, 1 Mar 2021 10:24:32 +0100
Subject: docs/devel/qgraph: improve qgraph documentation

Improve current qgraph documentation with a more concrete example
and clearer motivation.

This patch depends on the previous serie
"libqos/qgraph: format qgraph comments for sphinx documentation"

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210301092432.20342-1-eesposit@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 docs/devel/qgraph.rst | 509 ++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 408 insertions(+), 101 deletions(-)

(limited to 'docs/devel')

diff --git a/docs/devel/qgraph.rst b/docs/devel/qgraph.rst
index 62a45cbcbf..a9aff167ad 100644
--- a/docs/devel/qgraph.rst
+++ b/docs/devel/qgraph.rst
@@ -4,14 +4,37 @@
 Qtest Driver Framework
 ========================================
 
-This Qgraph API provides all basic functions to create a graph
-and instantiate nodes representing machines, drivers and tests
-representing their relations with ``CONSUMES``, ``PRODUCES``, and
-``CONTAINS`` edges.
+In order to test a specific driver, plain libqos tests need to
+take care of booting QEMU with the right machine and devices.
+This makes each test "hardcoded" for a specific configuration, reducing
+the possible coverage that it can reach.
+
+For example, the sdhci device is supported on both x86_64 and ARM boards,
+therefore a generic sdhci test should test all machines and drivers that
+support that device.
+Using only libqos APIs, the test has to manually take care of
+covering all the setups, and build the correct command line.
+
+This also introduces backward compability issues: if a device/driver command
+line name is changed, all tests that use that will not work
+properly anymore and need to be adjusted.
+
+The aim of qgraph is to create a graph of drivers, machines and tests such that
+a test aimed to a certain driver does not have to care of
+booting the right QEMU machine, pick the right device, build the command line
+and so on. Instead, it only defines what type of device it is testing
+(interface in qgraph terms) and the framework takes care of
+covering all supported types of devices and machine architectures.
+
+Following the above example, an interface would be ``sdhci``,
+so the sdhci-test should only care of linking its qgraph node with
+that interface. In this way, if the command line of a sdhci driver
+is changed, only the respective qgraph driver node has to be adjusted.
+
+The graph is composed by nodes that represent machines, drivers, tests
+and edges that define the relationships between them (``CONSUMES``, ``PRODUCES``, and
+``CONTAINS``).
 
-The idea is to have a framework where each test asks for a specific
-driver, and the framework takes care of allocating the proper devices
-required and passing the correct command line arguments to QEMU.
 
 Nodes
 ^^^^^^
@@ -24,8 +47,11 @@ A node can be of four types:
   drivers).
   An interface is not explicitly created, it will be automatically
   instantiated when a node consumes or produces it.
-- **QNODE_TEST**:      for example ``sdhci-test``, consumes an interface and
-  tests the functions provided.
+  An interface is simply a struct that abstracts the various drivers
+  for the same type of device, and offers an API to the nodes that
+  use it ("consume" relation in qgraph terms) that is implemented/backed up by the drivers that implement it ("produce" relation in qgraph terms).
+- **QNODE_TEST**:      for example ``sdhci-test``. A test consumes an interface
+  and tests the functions provided by it.
 
 Notes for the nodes:
 
@@ -69,136 +95,415 @@ available and only test that are reached by them will be executed.
 Creating a new driver and its interface
 """""""""""""""""""""""""""""""""""""""""
 
-.. code::
+Here we continue the ``sdhci`` use case, with the following scenario:
+
+- ``sdhci-test`` aims to test the ``read[q,w], writeq`` functions
+  offered by the ``sdhci`` drivers.
+- The current ``sdhci`` device is supported by both ``x86_64/pc`` and ``ARM``
+  (in this example we focus on the ``arm-raspi2``) machines.
+- QEMU offers 2 types of drivers: ``QSDHCI_MemoryMapped`` for ``ARM`` and
+  ``QSDHCI_PCI`` for ``x86_64/pc``. Both implement the
+  ``read[q,w], writeq`` functions.
+
+In order to implement such scenario in qgraph, the test developer needs to:
+
+- Create the ``x86_64/pc`` machine node. This machine uses the
+  ``pci-bus`` architecture so it ``contains`` a PCI driver,
+  ``pci-bus-pc``. The actual path is
+
+  ``x86_64/pc --contains--> 1440FX-pcihost --contains-->
+  pci-bus-pc --produces--> pci-bus``.
+
+  For the sake of this example,
+  we do not focus on the PCI interface implementation.
+- Create the ``sdhci-pci`` driver node, representing ``QSDHCI_PCI``.
+  The driver uses the PCI bus (and its API),
+  so it must ``consume`` the ``pci-bus`` generic interface (which abstracts
+  all the pci drivers available)
+
+  ``sdhci-pci --consumes--> pci-bus``
+- Create an ``arm/raspi2`` machine node. This machine ``contains``
+  a ``generic-sdhci`` memory mapped ``sdhci`` driver node, representing
+  ``QSDHCI_MemoryMapped``.
+
+  ``arm/raspi2 --contains--> generic-sdhci``
+- Create the ``sdhci`` interface node. This interface offers the
+  functions that are shared by all ``sdhci`` devices.
+  The interface is produced by ``sdhci-pci`` and ``generic-sdhci``,
+  the available architecture-specific drivers.
+
+  ``sdhci-pci --produces--> sdhci``
+
+  ``generic-sdhci --produces--> sdhci``
+- Create the ``sdhci-test`` test node. The test ``consumes`` the
+  ``sdhci`` interface, using its API. It doesn't need to look at
+  the supported machines or drivers.
+
+  ``sdhci-test --consumes--> sdhci``
+
+``arm-raspi2`` machine, simplified from
+``tests/qtest/libqos/arm-raspi2-machine.c``::
 
     #include "qgraph.h"
 
-    struct My_driver {
+    struct QRaspi2Machine {
         QOSGraphObject obj;
-        Node_produced prod;
-        Node_contained cont;
+        QGuestAllocator alloc;
+        QSDHCI_MemoryMapped sdhci;
+    };
+
+    static void *raspi2_get_driver(void *object, const char *interface)
+    {
+        QRaspi2Machine *machine = object;
+        if (!g_strcmp0(interface, "memory")) {
+            return &machine->alloc;
+        }
+
+        fprintf(stderr, "%s not present in arm/raspi2\n", interface);
+        g_assert_not_reached();
+    }
+
+    static QOSGraphObject *raspi2_get_device(void *obj,
+                                                const char *device)
+    {
+        QRaspi2Machine *machine = obj;
+        if (!g_strcmp0(device, "generic-sdhci")) {
+            return &machine->sdhci.obj;
+        }
+
+        fprintf(stderr, "%s not present in arm/raspi2\n", device);
+        g_assert_not_reached();
     }
 
-    static void my_destructor(QOSGraphObject *obj)
+    static void *qos_create_machine_arm_raspi2(QTestState *qts)
     {
-        g_free(obj);
+        QRaspi2Machine *machine = g_new0(QRaspi2Machine, 1);
+
+        alloc_init(&machine->alloc, ...);
+
+        /* Get node(s) contained inside (CONTAINS) */
+        machine->obj.get_device = raspi2_get_device;
+
+        /* Get node(s) produced (PRODUCES) */
+        machine->obj.get_driver = raspi2_get_driver;
+
+        /* free the object */
+        machine->obj.destructor = raspi2_destructor;
+        qos_init_sdhci_mm(&machine->sdhci, ...);
+        return &machine->obj;
     }
 
-    static void *my_get_driver(void *object, const char *interface) {
-        My_driver *dev = object;
-        if (!g_strcmp0(interface, "my_interface")) {
-            return &dev->prod;
+    static void raspi2_register_nodes(void)
+    {
+        /* arm/raspi2 --contains--> generic-sdhci */
+        qos_node_create_machine("arm/raspi2",
+                                 qos_create_machine_arm_raspi2);
+        qos_node_contains("arm/raspi2", "generic-sdhci", NULL);
+    }
+
+    libqos_init(raspi2_register_nodes);
+
+``x86_64/pc`` machine, simplified from
+``tests/qtest/libqos/x86_64_pc-machine.c``::
+
+    #include "qgraph.h"
+
+    struct i440FX_pcihost {
+        QOSGraphObject obj;
+        QPCIBusPC pci;
+    };
+
+    struct QX86PCMachine {
+        QOSGraphObject obj;
+        QGuestAllocator alloc;
+        i440FX_pcihost bridge;
+    };
+
+    /* i440FX_pcihost */
+
+    static QOSGraphObject *i440FX_host_get_device(void *obj,
+                                                const char *device)
+    {
+        i440FX_pcihost *host = obj;
+        if (!g_strcmp0(device, "pci-bus-pc")) {
+            return &host->pci.obj;
+        }
+        fprintf(stderr, "%s not present in i440FX-pcihost\n", device);
+        g_assert_not_reached();
+    }
+
+    /* x86_64/pc machine */
+
+    static void *pc_get_driver(void *object, const char *interface)
+    {
+        QX86PCMachine *machine = object;
+        if (!g_strcmp0(interface, "memory")) {
+            return &machine->alloc;
         }
-        abort();
+
+        fprintf(stderr, "%s not present in x86_64/pc\n", interface);
+        g_assert_not_reached();
     }
 
-    static void *my_get_device(void *object, const char *device) {
-        My_driver *dev = object;
-        if (!g_strcmp0(device, "my_driver_contained")) {
-            return &dev->cont;
+    static QOSGraphObject *pc_get_device(void *obj, const char *device)
+    {
+        QX86PCMachine *machine = obj;
+        if (!g_strcmp0(device, "i440FX-pcihost")) {
+            return &machine->bridge.obj;
         }
-        abort();
+
+        fprintf(stderr, "%s not present in x86_64/pc\n", device);
+        g_assert_not_reached();
     }
 
-    static void *my_driver_constructor(void *node_consumed,
-                                        QOSGraphObject *alloc)
+    static void *qos_create_machine_pc(QTestState *qts)
     {
-        My_driver dev = g_new(My_driver, 1);
+        QX86PCMachine *machine = g_new0(QX86PCMachine, 1);
 
-        // get the node pointed by the produce edge
-        dev->obj.get_driver = my_get_driver;
+        /* Get node(s) contained inside (CONTAINS) */
+        machine->obj.get_device = pc_get_device;
 
-        // get the node pointed by the contains
-        dev->obj.get_device = my_get_device;
+        /* Get node(s) produced (PRODUCES) */
+        machine->obj.get_driver = pc_get_driver;
 
-        // free the object
-        dev->obj.destructor = my_destructor;
+        /* free the object */
+        machine->obj.destructor = pc_destructor;
+        pc_alloc_init(&machine->alloc, qts, ALLOC_NO_FLAGS);
 
-        do_something_with_node_consumed(node_consumed);
+        /* Get node(s) contained inside (CONTAINS) */
+        machine->bridge.obj.get_device = i440FX_host_get_device;
 
-        // set all fields of contained device
-        init_contained_device(&dev->cont);
-        return &dev->obj;
+        return &machine->obj;
     }
 
-    static void register_my_driver(void)
+    static void pc_machine_register_nodes(void)
     {
-        qos_node_create_driver("my_driver", my_driver_constructor);
-
-        // contained drivers don't need a constructor,
-        // they will be init by the parent.
-        qos_node_create_driver("my_driver_contained", NULL);
-
-        // For the sake of this example, assume machine x86_64/pc
-        // contains "other_node".
-        // This relation, along with the machine and "other_node"
-        // creation, should be defined in the x86_64_pc-machine.c file.
-        // "my_driver" will then consume "other_node"
-        qos_node_contains("my_driver", "my_driver_contained");
-        qos_node_produces("my_driver", "my_interface");
-        qos_node_consumes("my_driver", "other_node");
+        /* x86_64/pc --contains--> 1440FX-pcihost --contains-->
+         * pci-bus-pc [--produces--> pci-bus (in pci.h)] */
+        qos_node_create_machine("x86_64/pc", qos_create_machine_pc);
+        qos_node_contains("x86_64/pc", "i440FX-pcihost", NULL);
+
+        /* contained drivers don't need a constructor,
+         * they will be init by the parent */
+        qos_node_create_driver("i440FX-pcihost", NULL);
+        qos_node_contains("i440FX-pcihost", "pci-bus-pc", NULL);
     }
 
-In the above example, all possible types of relations are created:
-node "my_driver" consumes, contains and produces other nodes.
-More specifically::
+    libqos_init(pc_machine_register_nodes);
 
-  x86_64/pc -->contains--> other_node <--consumes-- my_driver
-                                                        |
-                       my_driver_contained <--contains--+
-                                                        |
-                              my_interface <--produces--+
+``sdhci`` taken from ``tests/qtest/libqos/sdhci.c``::
 
-or inverting the consumes edge in consumed_by::
+    /* Interface node, offers the sdhci API */
+    struct QSDHCI {
+        uint16_t (*readw)(QSDHCI *s, uint32_t reg);
+        uint64_t (*readq)(QSDHCI *s, uint32_t reg);
+        void (*writeq)(QSDHCI *s, uint32_t reg, uint64_t val);
+        /* other fields */
+    };
 
-  x86_64/pc -->contains--> other_node --consumed_by--> my_driver
-                                                            |
-                           my_driver_contained <--contains--+
+    /* Memory Mapped implementation of QSDHCI */
+    struct QSDHCI_MemoryMapped {
+        QOSGraphObject obj;
+        QSDHCI sdhci;
+        /* other driver-specific fields */
+    };
+
+    /* PCI implementation of QSDHCI */
+    struct QSDHCI_PCI {
+        QOSGraphObject obj;
+        QSDHCI sdhci;
+        /* other driver-specific fields */
+    };
+
+    /* Memory mapped implementation of QSDHCI */
+
+    static void *sdhci_mm_get_driver(void *obj, const char *interface)
+    {
+        QSDHCI_MemoryMapped *smm = obj;
+        if (!g_strcmp0(interface, "sdhci")) {
+            return &smm->sdhci;
+        }
+        fprintf(stderr, "%s not present in generic-sdhci\n", interface);
+        g_assert_not_reached();
+    }
+
+    void qos_init_sdhci_mm(QSDHCI_MemoryMapped *sdhci, QTestState *qts,
+                        uint32_t addr, QSDHCIProperties *common)
+    {
+        /* Get node contained inside (CONTAINS) */
+        sdhci->obj.get_driver = sdhci_mm_get_driver;
+
+        /* SDHCI interface API */
+        sdhci->sdhci.readw = sdhci_mm_readw;
+        sdhci->sdhci.readq = sdhci_mm_readq;
+        sdhci->sdhci.writeq = sdhci_mm_writeq;
+        sdhci->qts = qts;
+    }
+
+    /* PCI implementation of QSDHCI */
+
+    static void *sdhci_pci_get_driver(void *object,
+                                      const char *interface)
+    {
+        QSDHCI_PCI *spci = object;
+        if (!g_strcmp0(interface, "sdhci")) {
+            return &spci->sdhci;
+        }
+
+        fprintf(stderr, "%s not present in sdhci-pci\n", interface);
+        g_assert_not_reached();
+    }
+
+    static void *sdhci_pci_create(void *pci_bus,
+                                  QGuestAllocator *alloc,
+                                  void *addr)
+    {
+        QSDHCI_PCI *spci = g_new0(QSDHCI_PCI, 1);
+        QPCIBus *bus = pci_bus;
+        uint64_t barsize;
+
+        qpci_device_init(&spci->dev, bus, addr);
+
+        /* SDHCI interface API */
+        spci->sdhci.readw = sdhci_pci_readw;
+        spci->sdhci.readq = sdhci_pci_readq;
+        spci->sdhci.writeq = sdhci_pci_writeq;
+
+        /* Get node(s) produced (PRODUCES) */
+        spci->obj.get_driver = sdhci_pci_get_driver;
+
+        spci->obj.start_hw = sdhci_pci_start_hw;
+        spci->obj.destructor = sdhci_destructor;
+        return &spci->obj;
+    }
+
+    static void qsdhci_register_nodes(void)
+    {
+        QOSGraphEdgeOptions opts = {
+            .extra_device_opts = "addr=04.0",
+        };
+
+        /* generic-sdhci */
+        /* generic-sdhci --produces--> sdhci */
+        qos_node_create_driver("generic-sdhci", NULL);
+        qos_node_produces("generic-sdhci", "sdhci");
+
+        /* sdhci-pci */
+        /* sdhci-pci --produces--> sdhci
+         * sdhci-pci --consumes--> pci-bus */
+        qos_node_create_driver("sdhci-pci", sdhci_pci_create);
+        qos_node_produces("sdhci-pci", "sdhci");
+        qos_node_consumes("sdhci-pci", "pci-bus", &opts);
+    }
+
+    libqos_init(qsdhci_register_nodes);
+
+In the above example, all possible types of relations are created::
+
+  x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
                                                             |
-                                  my_interface <--produces--+
+               sdhci-pci --consumes--> pci-bus <--produces--+
+                  |
+                  +--produces--+
+                               |
+                               v
+                             sdhci
+                               ^
+                               |
+                               +--produces-- +
+                                             |
+               arm/raspi2 --contains--> generic-sdhci
+
+or inverting the consumes edge in consumed_by::
 
-Creating new test
+  x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
+                                                            |
+            sdhci-pci <--consumed by-- pci-bus <--produces--+
+                |
+                +--produces--+
+                             |
+                             v
+                            sdhci
+                             ^
+                             |
+                             +--produces-- +
+                                           |
+            arm/raspi2 --contains--> generic-sdhci
+
+Adding a new test
 """""""""""""""""
 
-.. code::
+Given the above setup, adding a new test is very simple.
+``sdhci-test``, taken from ``tests/qtest/sdhci-test.c``::
 
-    #include "qgraph.h"
+    static void check_capab_sdma(QSDHCI *s, bool supported)
+    {
+        uint64_t capab, capab_sdma;
 
-    static void my_test_function(void *obj, void *data)
+        capab = s->readq(s, SDHC_CAPAB);
+        capab_sdma = FIELD_EX64(capab, SDHC_CAPAB, SDMA);
+        g_assert_cmpuint(capab_sdma, ==, supported);
+    }
+
+    static void test_registers(void *obj, void *data,
+                                QGuestAllocator *alloc)
     {
-        Node_produced *interface_to_test = obj;
-        // test interface_to_test
+        QSDHCI *s = obj;
+
+        /* example test */
+        check_capab_sdma(s, s->props.capab.sdma);
     }
 
-    static void register_my_test(void)
+    static void register_sdhci_test(void)
     {
-        qos_add_test("my_interface", "my_test", my_test_function);
+        /* sdhci-test --consumes--> sdhci */
+        qos_add_test("registers", "sdhci", test_registers, NULL);
     }
 
-    libqos_init(register_my_test);
+    libqos_init(register_sdhci_test);
 
-Here a new test is created, consuming "my_interface" node
-and creating a valid path from a machine to a test.
+Here a new test is created, consuming ``sdhci`` interface node
+and creating a valid path from both machines to a test.
 Final graph will be like this::
 
-  x86_64/pc --contains--> other_node <--consumes-- my_driver
-                                                         |
-                        my_driver_contained <--contains--+
-                                                         |
-         my_test --consumes--> my_interface <--produces--+
+  x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
+                                                            |
+               sdhci-pci --consumes--> pci-bus <--produces--+
+                  |
+                  +--produces--+
+                               |
+                               v
+                             sdhci <--consumes-- sdhci-test
+                               ^
+                               |
+                               +--produces-- +
+                                             |
+               arm/raspi2 --contains--> generic-sdhci
 
 or inverting the consumes edge in consumed_by::
 
-  x86_64/pc --contains--> other_node --consumed_by--> my_driver
-                                                            |
-                           my_driver_contained <--contains--+
+  x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
                                                             |
-         my_test <--consumed_by-- my_interface <--produces--+
+            sdhci-pci <--consumed by-- pci-bus <--produces--+
+                |
+                +--produces--+
+                             |
+                             v
+                            sdhci --consumed by--> sdhci-test
+                             ^
+                             |
+                             +--produces-- +
+                                           |
+            arm/raspi2 --contains--> generic-sdhci
 
 Assuming there the binary is
 ``QTEST_QEMU_BINARY=./qemu-system-x86_64``
 a valid test path will be:
-``/x86_64/pc/other_node/my_driver/my_interface/my_test``.
+``/x86_64/pc/1440FX-pcihost/pci-bus-pc/pci-bus/sdhci-pc/sdhci/sdhci-test``
+
+and for the binary ``QTEST_QEMU_BINARY=./qemu-system-arm``:
+
+``/arm/raspi2/generic-sdhci/sdhci/sdhci-test``
 
 Additional examples are also in ``test-qgraph.c``
 
@@ -215,19 +520,19 @@ There are three types of command line arguments:
   ``-device <device>``. It is automatically done by the framework.
 - ``after node``   : added as additional argument to the node name.
   This argument is added optionally when creating edges,
-  by setting the parameter @after_cmd_line and
-  @extra_edge_opts in #QOSGraphEdgeOptions.
+  by setting the parameter ``after_cmd_line`` and
+  ``extra_edge_opts`` in ``QOSGraphEdgeOptions``.
   The framework automatically adds
-  a comma before @extra_edge_opts,
+  a comma before ``extra_edge_opts``,
   because it is going to add attributes
   after the destination node pointed by
   the edge containing these options, and automatically
-  adds a space before @after_cmd_line, because it
+  adds a space before ``after_cmd_line``, because it
   adds an additional device, not an attribute.
 - ``before node``  : added as additional argument to the node name.
   This argument is added optionally when creating edges,
-  by setting the parameter @before_cmd_line in
-  #QOSGraphEdgeOptions. This attribute
+  by setting the parameter ``before_cmd_line`` in
+  ``QOSGraphEdgeOptions``. This attribute
   is going to add attributes before the destination node
   pointed by the edge containing these options. It is
   helpful to commands that are not node-representable,
@@ -243,17 +548,19 @@ devices to be added in QEMU.
 Example::
 
     QOSGraphEdgeOptions opts = {
-        .arg = NULL,
-        .size_arg = 0,
-        .after_cmd_line = "-device other",
-        .before_cmd_line = "-netdev something",
-        .extra_edge_opts = "addr=04.0",
+        .before_cmd_line = "-drive id=drv0,if=none,file=null-co://,"
+                           "file.read-zeroes=on,format=raw",
+        .after_cmd_line = "-device scsi-hd,bus=vs0.0,drive=drv0",
+
+        opts.extra_device_opts = "id=vs0";
     };
-    QOSGraphNodeS *node = qos_node_create_driver("my_node", constructor);
-    qos_node_consumes_args("my_node", "interface", &opts);
+
+    qos_node_create_driver("virtio-scsi-device",
+                            virtio_scsi_device_create);
+    qos_node_consumes("virtio-scsi-device", "virtio-bus", &opts);
 
 Will produce the following command line:
-``-netdev something -device my_node,addr=04.0 -device other``
+``-drive id=drv0,if=none,file=null-co://, -device virtio-scsi-device,id=vs0 -device scsi-hd,bus=vs0.0,drive=drv0``
 
 Qgraph API reference
 ^^^^^^^^^^^^^^^^^^^^
-- 
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