hwstub lib: Introduce framework for device filtering

The rationale behind this was ability to filter usb device by
bus numer and device address. This allows to connect with selected
device in case there is more then one  connected device implementing
hwstub interface. For now only USB backend makes use of this
but the foundation is generic and can be easily extended to other
backends.

Change-Id: I618cfdeeb09162d5fa1002db00e40ea17c43e727

2 files changed, 73 insertions, 13 deletions

diff --git a/utils/hwstub/lib/hwstub_uri.cpp b/utils/hwstub/lib/hwstub_uri.cpp
index e2f252f3dc..e940fe69e2 100644
--- a/utils/hwstub/lib/hwstub_uri.cpp
+++ b/utils/hwstub/lib/hwstub_uri.cpp
@@ -48,8 +48,12 @@ void print_usage(FILE *f, bool client, bool server)
     fprintf(f, "  default   Default choice made by the library\n");
     if(client)
     {
-        fprintf(f, "When creating a USB context, the domain and port must be empty:\n");
-        fprintf(f, "  usb:\n");
+        fprintf(f, "When creating a USB context, the domain and port represent usb_port and device_address\n");
+        fprintf(f, "as reported by lsusb. You can leave empty usb_port:device_address to match any usb device\n");
+        fprintf(f, "which provide hwstub interface\n");
+        fprintf(f, "  usb://\n");
+        fprintf(f, "or\n");
+        fprintf(f, "  usb://usb_port:device_address\n");
     }
     fprintf(f, "When creating a TCP context, the domain and port are the usual TCP parameters:\n");
     fprintf(f, "  tcp://localhost\n");
@@ -220,17 +224,55 @@ std::shared_ptr<context> create_context(const uri& uri, std::string *error)
     /* handle different types of contexts */
     if(uri.scheme() == "usb")
     {
-        /* domain and port must be empty */
-        if(!uri.domain().empty() || !uri.port().empty())
+        if(!uri.domain().empty() && !uri.port().empty())
+        {
+            /** URI usb://usb_port:device_address
+             *  for example usb://6:31
+             *  usb_port and device_address match numbers
+             *  reported by lsusb
+             *
+             *  This filtering is additional to filtering
+             *  by hwstub interface so final outcome will be device
+             *  with usb_port:device_address which IS hwstub device
+             */
+            try
+            {
+                int bus = std::stoi(uri.domain());
+                int addr = std::stoi(uri.port());
+                libusb_context *ctx;
+                libusb_init(&ctx);
+
+                /** Build closure used to filter valid devices */
+                std::function<bool(void *)> f = [bus, addr](void *d){
+                    libusb_device *dev = (libusb_device *)d;
+                    return hwstub::usb::device::is_bus_addr_device(dev, bus, addr);
+                };
+
+                return hwstub::usb::context::create(ctx, true, nullptr, f);
+            }
+            catch(...)
+            {
+                if(error)
+                    *error = "USB URI bus_port:device_address format error";
+                return std::shared_ptr<context>();
+            }
+        }
+        else if(uri.domain().empty() && uri.port().empty())
+        {
+            /** URI usb://
+             *  No filtering, any usb device with hwstub
+             *  interface will match
+             */
+            libusb_context *ctx;
+            libusb_init(&ctx);
+            return hwstub::usb::context::create(ctx, true);
+        }
+        else
         {
             if(error)
-            *error = "USB URI cannot contain a domain or a port";
+                *error = "USB URI format error";
             return std::shared_ptr<context>();
         }
-        /* in doubt, create a new libusb context and let the context destroy it */
-        libusb_context *ctx;
-        libusb_init(&ctx);
-        return hwstub::usb::context::create(ctx, true);
     }
     else if(uri.scheme() == "virt")
     {
diff --git a/utils/hwstub/lib/hwstub_usb.cpp b/utils/hwstub/lib/hwstub_usb.cpp
index e8b8e7bc3d..e6679ff780 100644
--- a/utils/hwstub/lib/hwstub_usb.cpp
+++ b/utils/hwstub/lib/hwstub_usb.cpp
@@ -41,20 +41,28 @@ context::context(libusb_context *ctx, bool cleanup_ctx)
 {
 }
 
+context::context(libusb_context *ctx, bool cleanup_ctx, std::string *error, device_filter_t f)
+    :m_usb_ctx(ctx), m_cleanup_ctx(cleanup_ctx)
+{
+    (void)error;
+    // NOTE: can't use initializer list since this member is from parent class
+    // and parent's class constructor is NOT called when initializer list is built
+    device_filter = f;
+}
+
 context::~context()
 {
     if(m_cleanup_ctx)
         libusb_exit(m_usb_ctx);
 }
 
-std::shared_ptr<context> context::create(libusb_context *ctx, bool cleanup_ctx,
-    std::string *error)
+std::shared_ptr<context> context::create(libusb_context *ctx, bool cleanup_ctx, std::string *error, device_filter_t f)
 {
     (void) error;
     if(ctx == nullptr)
         libusb_init(nullptr);
     // NOTE: can't use make_shared() because of the protected ctor */
-    return std::shared_ptr<context>(new context(ctx, cleanup_ctx));
+    return std::shared_ptr<context>(new context(ctx, cleanup_ctx, nullptr, f));
 }
 
 libusb_context *context::native_context()
@@ -81,7 +89,11 @@ error context::fetch_device_list(std::vector<ctx_dev_t>& list, void*& ptr)
     ptr = (void *)usb_list;
     list.clear();
     for(int i = 0; i < ret; i++)
-        if(device::is_hwstub_dev(usb_list[i]))
+        /* filter devices by hwstub interface and by other filtering criteria
+         * if provided
+         */
+        if(device::is_hwstub_dev(usb_list[i]) &&
+           context::device_filter(usb_list[i]))
             list.push_back(to_ctx_dev(usb_list[i]));
     return error::SUCCESS;
 }
@@ -231,6 +243,12 @@ uint16_t device::get_pid()
     return dev_desc.idProduct;
 }
 
+bool device::is_bus_addr_device(libusb_device *dev, uint8_t bus, uint8_t addr)
+{
+    return ((libusb_get_bus_number(dev) == bus) &&
+            (libusb_get_device_address(dev) == addr));
+}
+
 /**
  * USB handle
  */