libusbhost: permits client polling on inotify wd

Modify libusbhost to expose the inotify watch descriptor to clients

This modification permits clients to add the watch descriptor to
their polling loop so that they don't have to use a dedicated
thread only for libusbhost.

Change-Id: I615bfcd56beab978135034b228d4d93337351eab
Signed-off-by: Guillaume Ranquet <guillaumex.ranquet@intel.com>
Signed-off-by: Luc Piguet-Lacroix <lucx.piguet-lacroix@intel.com>

1 files changed, 105 insertions, 65 deletions

diff --git a/libusbhost/usbhost.c b/libusbhost/usbhost.c
index c059b89..167fa60 100644
--- a/libusbhost/usbhost.c
+++ b/libusbhost/usbhost.c
@@ -33,6 +33,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <stddef.h>
 
 #include <sys/ioctl.h>
 #include <sys/types.h>
@@ -50,16 +51,23 @@
 #include "usbhost/usbhost.h"
 
 #define DEV_DIR             "/dev"
-#define USB_FS_DIR          "/dev/bus/usb"
-#define USB_FS_ID_SCANNER   "/dev/bus/usb/%d/%d"
-#define USB_FS_ID_FORMAT    "/dev/bus/usb/%03d/%03d"
+#define USB_FS_DIR          DEV_DIR "/bus/usb"
+#define USB_FS_ID_SCANNER   USB_FS_DIR "/%d/%d"
+#define USB_FS_ID_FORMAT    USB_FS_DIR "/%03d/%03d"
 
 // From drivers/usb/core/devio.c
 // I don't know why this isn't in a kernel header
 #define MAX_USBFS_BUFFER_SIZE   16384
 
+#define MAX_USBFS_WD_COUNT      10
+
 struct usb_host_context {
-    int fd;
+    int                         fd;
+    usb_device_added_cb         cb_added;
+    usb_device_removed_cb       cb_removed;
+    void                        *data;
+    int                         wds[MAX_USBFS_WD_COUNT];
+    int                         wdd;
 };
 
 struct usb_device {
@@ -116,10 +124,10 @@ static int find_existing_devices(usb_device_added_cb added_cb,
     while ((de = readdir(busdir)) != 0 && !done) {
         if(badname(de->d_name)) continue;
 
-        snprintf(busname, sizeof(busname), "%s/%s", USB_FS_DIR, de->d_name);
+        snprintf(busname, sizeof(busname), USB_FS_DIR "/%s", de->d_name);
         done = find_existing_devices_bus(busname, added_cb,
                                          client_data);
-    }
+    } //end of busdir while
     closedir(busdir);
 
     return done;
@@ -137,7 +145,7 @@ static void watch_existing_subdirs(struct usb_host_context *context,
 
     /* watch existing subdirectories of USB_FS_DIR */
     for (i = 1; i < wd_count; i++) {
-        snprintf(path, sizeof(path), "%s/%03d", USB_FS_DIR, i);
+        snprintf(path, sizeof(path), USB_FS_DIR "/%03d", i);
         ret = inotify_add_watch(context->fd, path, IN_CREATE | IN_DELETE);
         if (ret >= 0)
             wds[i] = ret;
@@ -166,93 +174,126 @@ void usb_host_cleanup(struct usb_host_context *context)
     free(context);
 }
 
-void usb_host_run(struct usb_host_context *context,
+int usb_host_get_fd(struct usb_host_context *context)
+{
+    return context->fd;
+} /* usb_host_get_fd() */
+
+int usb_host_load(struct usb_host_context *context,
                   usb_device_added_cb added_cb,
                   usb_device_removed_cb removed_cb,
                   usb_discovery_done_cb discovery_done_cb,
                   void *client_data)
 {
-    struct inotify_event* event;
-    char event_buf[512];
-    char path[100];
-    int i, ret, done = 0;
-    int wd, wdd, wds[10];
-    int wd_count = sizeof(wds) / sizeof(wds[0]);
+    int done = 0;
+    int i;
+
+    context->cb_added = added_cb;
+    context->cb_removed = removed_cb;
+    context->data = client_data;
 
     D("Created device discovery thread\n");
 
     /* watch for files added and deleted within USB_FS_DIR */
-    for (i = 0; i < wd_count; i++)
-        wds[i] = -1;
+    for (i = 0; i < MAX_USBFS_WD_COUNT; i++)
+        context->wds[i] = -1;
 
     /* watch the root for new subdirectories */
-    wdd = inotify_add_watch(context->fd, DEV_DIR, IN_CREATE | IN_DELETE);
-    if (wdd < 0) {
+    context->wdd = inotify_add_watch(context->fd, DEV_DIR, IN_CREATE | IN_DELETE);
+    if (context->wdd < 0) {
         fprintf(stderr, "inotify_add_watch failed\n");
         if (discovery_done_cb)
             discovery_done_cb(client_data);
-        return;
+        return done;
     }
 
-    watch_existing_subdirs(context, wds, wd_count);
+    watch_existing_subdirs(context, context->wds, MAX_USBFS_WD_COUNT);
 
     /* check for existing devices first, after we have inotify set up */
     done = find_existing_devices(added_cb, client_data);
     if (discovery_done_cb)
         done |= discovery_done_cb(client_data);
 
-    while (!done) {
-        ret = read(context->fd, event_buf, sizeof(event_buf));
-        if (ret >= (int)sizeof(struct inotify_event)) {
-            event = (struct inotify_event *)event_buf;
-            wd = event->wd;
-            if (wd == wdd) {
-                if ((event->mask & IN_CREATE) && !strcmp(event->name, "bus")) {
-                    watch_existing_subdirs(context, wds, wd_count);
-                    done = find_existing_devices(added_cb, client_data);
-                } else if ((event->mask & IN_DELETE) && !strcmp(event->name, "bus")) {
-                    for (i = 0; i < wd_count; i++) {
-                        if (wds[i] >= 0) {
-                            inotify_rm_watch(context->fd, wds[i]);
-                            wds[i] = -1;
-                        }
+    return done;
+} /* usb_host_load() */
+
+int usb_host_read_event(struct usb_host_context *context)
+{
+    struct inotify_event* event;
+    char event_buf[512];
+    char path[100];
+    int i, ret, done = 0;
+    int j, event_size;
+    int wd;
+
+    ret = read(context->fd, event_buf, sizeof(event_buf));
+    if (ret >= (int)sizeof(struct inotify_event)) {
+        event = (struct inotify_event *)event_buf;
+        wd = event->wd;
+        if (wd == context->wdd) {
+            if ((event->mask & IN_CREATE) && !strcmp(event->name, "bus")) {
+                watch_existing_subdirs(context, context->wds, MAX_USBFS_WD_COUNT);
+                done = find_existing_devices(context->cb_added, context->data);
+            } else if ((event->mask & IN_DELETE) && !strcmp(event->name, "bus")) {
+                for (i = 0; i < MAX_USBFS_WD_COUNT; i++) {
+                    if (context->wds[i] >= 0) {
+                        inotify_rm_watch(context->fd, context->wds[i]);
+                        context->wds[i] = -1;
                     }
                 }
-            } else if (wd == wds[0]) {
-                i = atoi(event->name);
-                snprintf(path, sizeof(path), "%s/%s", USB_FS_DIR, event->name);
-                D("%s subdirectory %s: index: %d\n", (event->mask & IN_CREATE) ?
-                                                     "new" : "gone", path, i);
-                if (i > 0 && i < wd_count) {
-                    if (event->mask & IN_CREATE) {
-                        ret = inotify_add_watch(context->fd, path,
-                                                IN_CREATE | IN_DELETE);
-                        if (ret >= 0)
-                            wds[i] = ret;
-                        done = find_existing_devices_bus(path, added_cb,
-                                                         client_data);
-                    } else if (event->mask & IN_DELETE) {
-                        inotify_rm_watch(context->fd, wds[i]);
-                        wds[i] = -1;
-                    }
+            }
+        } else if (wd == context->wds[0]) {
+            i = atoi(event->name);
+            snprintf(path, sizeof(path), USB_FS_DIR "/%s", event->name);
+            D("%s subdirectory %s: index: %d\n", (event->mask & IN_CREATE) ?
+                    "new" : "gone", path, i);
+            if (i > 0 && i < MAX_USBFS_WD_COUNT) {
+                if (event->mask & IN_CREATE) {
+                    ret = inotify_add_watch(context->fd, path,
+                            IN_CREATE | IN_DELETE);
+                    if (ret >= 0)
+                        context->wds[i] = ret;
+                    done = find_existing_devices_bus(path, context->cb_added,
+                            context->data);
+                } else if (event->mask & IN_DELETE) {
+                    inotify_rm_watch(context->fd, context->wds[i]);
+                    context->wds[i] = -1;
                 }
-            } else {
-                for (i = 1; i < wd_count && !done; i++) {
-                    if (wd == wds[i]) {
-                        snprintf(path, sizeof(path), "%s/%03d/%s", USB_FS_DIR, i, event->name);
-                        if (event->mask == IN_CREATE) {
-                            D("new device %s\n", path);
-                            done = added_cb(path, client_data);
-                        } else if (event->mask == IN_DELETE) {
-                            D("gone device %s\n", path);
-                            done = removed_cb(path, client_data);
-                        }
+            }
+        } else {
+            for (i = 1; (i < MAX_USBFS_WD_COUNT) && !done; i++) {
+                if (wd == context->wds[i]) {
+                    snprintf(path, sizeof(path), USB_FS_DIR "/%03d/%s", i, event->name);
+                    if (event->mask == IN_CREATE) {
+                        D("new device %s\n", path);
+                        done = context->cb_added(path, context->data);
+                    } else if (event->mask == IN_DELETE) {
+                        D("gone device %s\n", path);
+                        done = context->cb_removed(path, context->data);
                     }
                 }
             }
         }
     }
-}
+
+    return done;
+} /* usb_host_read_event() */
+
+void usb_host_run(struct usb_host_context *context,
+                  usb_device_added_cb added_cb,
+                  usb_device_removed_cb removed_cb,
+                  usb_discovery_done_cb discovery_done_cb,
+                  void *client_data)
+{
+    int done;
+
+    done = usb_host_load(context, added_cb, removed_cb, discovery_done_cb, client_data);
+
+    while (!done) {
+
+        done = usb_host_read_event(context);
+    }
+} /* usb_host_run() */
 
 struct usb_device *usb_device_open(const char *dev_name)
 {
@@ -606,7 +647,6 @@ struct usb_request *usb_request_wait(struct usb_device *dev)
 {
     struct usbdevfs_urb *urb = NULL;
     struct usb_request *req = NULL;
-    int res;
 
     while (1) {
         int res = ioctl(dev->fd, USBDEVFS_REAPURB, &urb);