kern: iotap: Expose I/O taps to userland

Expose I/O taps to userland using a tap message interface. An
application may construct a tap message to send to the kernel requesting
data from a specific tap, if there is data, the buffers will be safely
populated, otherwise some error returned.

An example is accessing the PS/2 keyboard tap:

--

char name[] = "i8042.port.0";
char buf[2] = {0, 0};
struct iotap_msg msg = {
    .opcode = IOTAP_OPC_READ,
    .buf = buf,
    .len = len
};

...

/* muxtap() may be used */

...
--

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/sys/include/os/iotap.h b/src/sys/include/os/iotap.h
index 7421bf1..baef59c 100644
--- a/src/sys/include/os/iotap.h
+++ b/src/sys/include/os/iotap.h
@@ -32,6 +32,11 @@
 
 #include <sys/types.h>
 #include <sys/queue.h>
+#include <sys/iotap.h>
+#include <sys/syscall.h>
+#include <os/mac.h>
+
+#define IOTAP_MSG_MAX 1024
 
 struct iotap_desc;
 typedef int16_t iotap_t;
@@ -79,4 +84,21 @@ iotap_t iotap_register(const struct iotap_desc *iotap);
  */
 int iotap_lookup(const char *name, struct iotap_desc *dp_res);
 
+/*
+ * Handle an I/O tap message and perform operations
+ * using specific commands.
+ *
+ * @name: Name of tap to operate on
+ * @msg: Message to send
+ *
+ * Returns less than zero values on failure, other
+ * values depend on the input command.
+ */
+ssize_t iotap_mux(const char *name, struct iotap_msg *msg);
+
+/*
+ * Perform an operation on an I/O tap
+ */
+scret_t sys_muxtap(struct syscall_args *scargs);
+
 #endif  /* !_OS_IOTAP_H_ */