Commit 2c3269152a9b363b0b67c035f79a745b2791b2dc
2021-02-16T12:39:48
Use inotify for HIDAPI joystick enumeration if not using udev This improves SDL's ability to detect HIDAPI joystick hotplug in a container environment because we cannot reliably receive events from udev in a container. For a more detailed explanation of why this issue happens with containers, please check the previous commit "joystick: Use inotify to detect joystick unplug if not using udev" (b0eba1c5). Signed-off-by: Ludovico de Nittis <ludovico.denittis@collabora.com>
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diff --git a/src/joystick/hidapi/SDL_hidapijoystick.c b/src/joystick/hidapi/SDL_hidapijoystick.c
index e751bb1..25eb7b6 100644
--- a/src/joystick/hidapi/SDL_hidapijoystick.c
+++ b/src/joystick/hidapi/SDL_hidapijoystick.c
@@ -52,6 +52,13 @@
#ifdef SDL_USE_LIBUDEV
#include <poll.h>
#endif
+#ifdef HAVE_INOTIFY
+#include <errno.h> /* errno, strerror */
+#include <fcntl.h>
+#include <limits.h> /* For the definition of NAME_MAX */
+#include <sys/inotify.h>
+#include <unistd.h>
+#endif
#endif
typedef enum
@@ -101,6 +108,7 @@ static SDL_HIDAPI_Device *SDL_HIDAPI_devices;
static int SDL_HIDAPI_numjoysticks = 0;
static SDL_bool initialized = SDL_FALSE;
static SDL_bool shutting_down = SDL_FALSE;
+static int inotify_fd = -1;
#if defined(SDL_USE_LIBUDEV)
static const SDL_UDEV_Symbols * usyms = NULL;
@@ -194,6 +202,46 @@ static void CallbackIOServiceFunc(void *context, io_iterator_t portIterator)
}
#endif /* __MACOSX__ */
+#ifdef HAVE_INOTIFY
+#ifdef HAVE_INOTIFY_INIT1
+static int SDL_inotify_init1(void) {
+ return inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
+}
+#else
+static int SDL_inotify_init1(void) {
+ int fd = inotify_init();
+ if (fd < 0) return -1;
+ fcntl(fd, F_SETFL, O_NONBLOCK);
+ fcntl(fd, F_SETFD, FD_CLOEXEC);
+ return fd;
+}
+#endif
+
+static int
+StrHasPrefix(const char *string, const char *prefix)
+{
+ return (SDL_strncmp(string, prefix, SDL_strlen(prefix)) == 0);
+}
+
+static int
+StrIsInteger(const char *string)
+{
+ const char *p;
+
+ if (*string == '\0') {
+ return 0;
+ }
+
+ for (p = string; *p != '\0'; p++) {
+ if (*p < '0' || *p > '9') {
+ return 0;
+ }
+ }
+
+ return 1;
+}
+#endif
+
static void
HIDAPI_InitializeDiscovery()
{
@@ -301,7 +349,37 @@ HIDAPI_InitializeDiscovery()
}
}
}
+ else
#endif /* SDL_USE_LIBUDEV */
+ {
+#if defined(HAVE_INOTIFY)
+ inotify_fd = SDL_inotify_init1();
+
+ if (inotify_fd < 0) {
+ SDL_LogWarn(SDL_LOG_CATEGORY_INPUT,
+ "Unable to initialize inotify, falling back to polling: %s",
+ strerror(errno));
+ return;
+ }
+
+ /* We need to watch for attribute changes in addition to
+ * creation, because when a device is first created, it has
+ * permissions that we can't read. When udev chmods it to
+ * something that we maybe *can* read, we'll get an
+ * IN_ATTRIB event to tell us. */
+ if (inotify_add_watch(inotify_fd, "/dev",
+ IN_CREATE | IN_DELETE | IN_MOVE | IN_ATTRIB) < 0) {
+ close(inotify_fd);
+ inotify_fd = -1;
+ SDL_LogWarn(SDL_LOG_CATEGORY_INPUT,
+ "Unable to add inotify watch, falling back to polling: %s",
+ strerror (errno));
+ return;
+ }
+
+ SDL_HIDAPI_discovery.m_bCanGetNotifications = SDL_TRUE;
+#endif /* HAVE_INOTIFY */
+ }
}
static void
@@ -368,7 +446,49 @@ HIDAPI_UpdateDiscovery()
}
}
}
+ else
#endif /* SDL_USE_LIBUDEV */
+ {
+#if defined(HAVE_INOTIFY)
+ if (inotify_fd >= 0) {
+ union
+ {
+ struct inotify_event event;
+ char storage[4096];
+ char enough_for_inotify[sizeof (struct inotify_event) + NAME_MAX + 1];
+ } buf;
+ ssize_t bytes;
+ size_t remain = 0;
+ size_t len;
+
+ bytes = read(inotify_fd, &buf, sizeof (buf));
+
+ if (bytes > 0) {
+ remain = (size_t) bytes;
+ }
+
+ while (remain > 0) {
+ if (buf.event.len > 0 &&
+ !SDL_HIDAPI_discovery.m_bHaveDevicesChanged) {
+ if (StrHasPrefix(buf.event.name, "hidraw") &&
+ StrIsInteger(buf.event.name + strlen ("hidraw"))) {
+ SDL_HIDAPI_discovery.m_bHaveDevicesChanged = SDL_TRUE;
+ /* We found an hidraw change. We still continue to
+ * drain the inotify fd to avoid leaving old
+ * notifications in the queue. */
+ }
+ }
+
+ len = sizeof (struct inotify_event) + buf.event.len;
+ remain -= len;
+
+ if (remain != 0) {
+ memmove(&buf.storage[0], &buf.storage[len], remain);
+ }
+ }
+ }
+#endif /* HAVE_INOTIFY */
+ }
}
static void
@@ -1283,6 +1403,11 @@ HIDAPI_JoystickQuit(void)
SDL_HIDAPI_QuitRumble();
+ if (inotify_fd >= 0) {
+ close(inotify_fd);
+ inotify_fd = -1;
+ }
+
while (SDL_HIDAPI_devices) {
HIDAPI_DelDevice(SDL_HIDAPI_devices);
}