os: Add NotifyFd interfaces

This provides a callback-based interface to monitor file
descriptors beyond the usual client and device interfaces.

Modules within the server using file descriptors for reading and/or
writing can call

    Bool SetNotifyFd(int fd, NotifyFdProcPtr notify_fd, int mask, void *data);

mask can be any combination of X_NOTIFY_READ and X_NOTIFY_WRITE.

When 'fd' becomes readable or writable, the notify_fd function will be
called with the 'fd', the ready conditions and 'data' values as arguments,

When the module no longer needs to monitor the fd, it will call

    void RemoveNotifyFd(int fd);

RemoveNotifyFd may be called from the notify function.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/os.h b/include/os.h
index 9937f2ea5..aed2e2f99 100644
--- a/include/os.h
+++ b/include/os.h
@@ -154,6 +154,19 @@ extern _X_EXPORT void AddEnabledDevice(int /*fd */ );
 
 extern _X_EXPORT void RemoveEnabledDevice(int /*fd */ );
 
+typedef void (*NotifyFdProcPtr)(int fd, int ready, void *data);
+
+#define X_NOTIFY_NONE   0
+#define X_NOTIFY_READ   1
+#define X_NOTIFY_WRITE  2
+
+extern _X_EXPORT Bool SetNotifyFd(int fd, NotifyFdProcPtr notify_fd, int mask, void *data);
+
+static inline void RemoveNotifyFd(int fd)
+{
+    (void) SetNotifyFd(fd, NULL, X_NOTIFY_NONE, NULL);
+}
+
 extern _X_EXPORT int OnlyListenToOneClient(ClientPtr /*client */ );
 
 extern _X_EXPORT void ListenToAllClients(void);