[PATCH 1/8] tty: Define ASYNC_ replacement bits

[Peter Hurley]

Prepare for relocating kernel private state bits out of tty_port::flags
field; tty_port::flags field is not atomic and can become corrupted
by concurrent updates. It also suffers from the complication of sharing
in a userspace-visible field which must be masked.

Define new tty_port::iflags field and new, substitute bit definitions
for the former ASYNC_* flags.

Signed-off-by: Peter Hurley 
---
 include/linux/tty.h| 16 +++-
 include/uapi/linux/tty_flags.h |  9 -
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 89f9c91..4e0dbda0 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -228,7 +228,8 @@ struct tty_port {
int count;  /* Usage count */
wait_queue_head_t   open_wait;  /* Open waiters */
wait_queue_head_t   delta_msr_wait; /* Modem status change */
-   unsigned long   flags;  /* TTY flags ASY_*/
+   unsigned long   flags;  /* User TTY flags ASYNC_ */
+   unsigned long   iflags; /* Internal flags TTY_PORT_ */
unsigned char   console:1,  /* port is a console */
low_latency:1;  /* optional: tune for latency */
struct mutexmutex;  /* Locking */
@@ -242,6 +243,19 @@ struct tty_port {
struct kref kref;   /* Ref counter */
 };
 
+/* tty_port::iflags bits -- use atomic bit ops */
+#define TTY_PORT_INITIALIZED   0   /* device is initialized */
+#define TTY_PORT_SUSPENDED 1   /* device is suspended */
+#define TTY_PORT_ACTIVE2   /* device is open */
+
+/*
+ * uart drivers: use the uart_port::status field and the UPSTAT_* defines
+ * for s/w-based flow control steering and carrier detection status
+ */
+#define TTY_PORT_CTS_FLOW  3   /* h/w flow control enabled */
+#define TTY_PORT_CHECK_CD  4   /* carrier detect enabled */
+
+
 /*
  * Where all of the state associated with a tty is kept while the tty
  * is open.  Since the termios state should be kept even if the tty
diff --git a/include/uapi/linux/tty_flags.h b/include/uapi/linux/tty_flags.h
index 072e41e..8e1a436 100644
--- a/include/uapi/linux/tty_flags.h
+++ b/include/uapi/linux/tty_flags.h
@@ -32,7 +32,12 @@
 #define ASYNCB_MAGIC_MULTIPLIER16 /* Use special CLK or divisor */
 #define ASYNCB_LAST_USER   16
 
-/* Internal flags used only by kernel */
+/*
+ * Internal flags used only by kernel (read-only)
+ *
+ * WARNING: These flags are no longer used and have been superceded by the
+ * TTY_PORT_ flags in the iflags field (and not userspace-visible)
+ */
 #define ASYNCB_INITIALIZED 31 /* Serial port was initialized */
 #define ASYNCB_SUSPENDED   30 /* Serial port is suspended */
 #define ASYNCB_NORMAL_ACTIVE   29 /* Normal device is active */
@@ -44,6 +49,7 @@
 #define ASYNCB_CONS_FLOW   23 /* flow control for console  */
 #define ASYNCB_FIRST_KERNEL22
 
+/* Masks */
 #define ASYNC_HUP_NOTIFY   (1U << ASYNCB_HUP_NOTIFY)
 #define ASYNC_SUSPENDED(1U << ASYNCB_SUSPENDED)
 #define ASYNC_FOURPORT (1U << ASYNCB_FOURPORT)
@@ -72,6 +78,7 @@
 #define ASYNC_SPD_WARP (ASYNC_SPD_HI|ASYNC_SPD_SHI)
 #define ASYNC_SPD_MASK (ASYNC_SPD_HI|ASYNC_SPD_VHI|ASYNC_SPD_SHI)
 
+/* These flags are no longer used (and were always masked from userspace) */
 #define ASYNC_INITIALIZED  (1U << ASYNCB_INITIALIZED)
 #define ASYNC_NORMAL_ACTIVE(1U << ASYNCB_NORMAL_ACTIVE)
 #define ASYNC_BOOT_AUTOCONF(1U << ASYNCB_BOOT_AUTOCONF)
-- 
2.8.1

[PATCH 1/8] tty: Define ASYNC_ replacement bits

[Peter Hurley]

Prepare for relocating kernel private state bits out of tty_port::flags
field; tty_port::flags field is not atomic and can become corrupted
by concurrent updates. It also suffers from the complication of sharing
in a userspace-visible field which must be masked.

Define new tty_port::iflags field and new, substitute bit definitions
for the former ASYNC_* flags.

Signed-off-by: Peter Hurley 
---
 include/linux/tty.h| 16 +++-
 include/uapi/linux/tty_flags.h |  9 -
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 89f9c91..4e0dbda0 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -228,7 +228,8 @@ struct tty_port {
int count;  /* Usage count */
wait_queue_head_t   open_wait;  /* Open waiters */
wait_queue_head_t   delta_msr_wait; /* Modem status change */
-   unsigned long   flags;  /* TTY flags ASY_*/
+   unsigned long   flags;  /* User TTY flags ASYNC_ */
+   unsigned long   iflags; /* Internal flags TTY_PORT_ */
unsigned char   console:1,  /* port is a console */
low_latency:1;  /* optional: tune for latency */
struct mutexmutex;  /* Locking */
@@ -242,6 +243,19 @@ struct tty_port {
struct kref kref;   /* Ref counter */
 };
 
+/* tty_port::iflags bits -- use atomic bit ops */
+#define TTY_PORT_INITIALIZED   0   /* device is initialized */
+#define TTY_PORT_SUSPENDED 1   /* device is suspended */
+#define TTY_PORT_ACTIVE2   /* device is open */
+
+/*
+ * uart drivers: use the uart_port::status field and the UPSTAT_* defines
+ * for s/w-based flow control steering and carrier detection status
+ */
+#define TTY_PORT_CTS_FLOW  3   /* h/w flow control enabled */
+#define TTY_PORT_CHECK_CD  4   /* carrier detect enabled */
+
+
 /*
  * Where all of the state associated with a tty is kept while the tty
  * is open.  Since the termios state should be kept even if the tty
diff --git a/include/uapi/linux/tty_flags.h b/include/uapi/linux/tty_flags.h
index 072e41e..8e1a436 100644
--- a/include/uapi/linux/tty_flags.h
+++ b/include/uapi/linux/tty_flags.h
@@ -32,7 +32,12 @@
 #define ASYNCB_MAGIC_MULTIPLIER16 /* Use special CLK or divisor */
 #define ASYNCB_LAST_USER   16
 
-/* Internal flags used only by kernel */
+/*
+ * Internal flags used only by kernel (read-only)
+ *
+ * WARNING: These flags are no longer used and have been superceded by the
+ * TTY_PORT_ flags in the iflags field (and not userspace-visible)
+ */
 #define ASYNCB_INITIALIZED 31 /* Serial port was initialized */
 #define ASYNCB_SUSPENDED   30 /* Serial port is suspended */
 #define ASYNCB_NORMAL_ACTIVE   29 /* Normal device is active */
@@ -44,6 +49,7 @@
 #define ASYNCB_CONS_FLOW   23 /* flow control for console  */
 #define ASYNCB_FIRST_KERNEL22
 
+/* Masks */
 #define ASYNC_HUP_NOTIFY   (1U << ASYNCB_HUP_NOTIFY)
 #define ASYNC_SUSPENDED(1U << ASYNCB_SUSPENDED)
 #define ASYNC_FOURPORT (1U << ASYNCB_FOURPORT)
@@ -72,6 +78,7 @@
 #define ASYNC_SPD_WARP (ASYNC_SPD_HI|ASYNC_SPD_SHI)
 #define ASYNC_SPD_MASK (ASYNC_SPD_HI|ASYNC_SPD_VHI|ASYNC_SPD_SHI)
 
+/* These flags are no longer used (and were always masked from userspace) */
 #define ASYNC_INITIALIZED  (1U << ASYNCB_INITIALIZED)
 #define ASYNC_NORMAL_ACTIVE(1U << ASYNCB_NORMAL_ACTIVE)
 #define ASYNC_BOOT_AUTOCONF(1U << ASYNCB_BOOT_AUTOCONF)
-- 
2.8.1