tty: move tty_buffer definitions to new tty_buffer.h

tty.h is large enough currently. And I am slowly adding kernel-doc
documentation, so it grows to unmaintainable long mess. To avoid this,
split tty.h further into tty_buffer.h and move there tty_buffer-related
declarations and function prototypes.

Note that many of the tty_buffer.c function prototypes reside now in
tty_flip.h. But we cannot move struct tty_buffer & friends because:
* tty_insert_flip_char() in tty_flip.h needs both struct tty_port and
  struct tty_buffer defined.
* struct tty_port in tty_port.h needs struct tty_buffer defined.

So if we moved struct tty_buffer to tty_flip.h too, tty_flip.h would
need tty_port.h and that would need tty_flip.h (to have tty_buffer)
again. Hence we introduce new header tty_buffer.h here to break this
circular dependency.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723103147.18250-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/include/linux/tty_buffer.h b/include/linux/tty_buffer.h
new file mode 100644
index 000000000000..3b9d77604291
--- /dev/null
+++ b/include/linux/tty_buffer.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_TTY_BUFFER_H
+#define _LINUX_TTY_BUFFER_H
+
+#include <linux/atomic.h>
+#include <linux/llist.h>
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+
+struct tty_buffer {
+	union {
+		struct tty_buffer *next;
+		struct llist_node free;
+	};
+	int used;
+	int size;
+	int commit;
+	int read;
+	int flags;
+	/* Data points here */
+	unsigned long data[];
+};
+
+/* Values for .flags field of tty_buffer */
+#define TTYB_NORMAL	1	/* buffer has no flags buffer */
+
+static inline unsigned char *char_buf_ptr(struct tty_buffer *b, int ofs)
+{
+	return ((unsigned char *)b->data) + ofs;
+}
+
+static inline char *flag_buf_ptr(struct tty_buffer *b, int ofs)
+{
+	return (char *)char_buf_ptr(b, ofs) + b->size;
+}
+
+struct tty_bufhead {
+	struct tty_buffer *head;	/* Queue head */
+	struct work_struct work;
+	struct mutex	   lock;
+	atomic_t	   priority;
+	struct tty_buffer sentinel;
+	struct llist_head free;		/* Free queue head */
+	atomic_t	   mem_used;    /* In-use buffers excluding free list */
+	int		   mem_limit;
+	struct tty_buffer *tail;	/* Active buffer */
+};
+
+/*
+ * When a break, frame error, or parity error happens, these codes are
+ * stuffed into the flags buffer.
+ */
+#define TTY_NORMAL	0
+#define TTY_BREAK	1
+#define TTY_FRAME	2
+#define TTY_PARITY	3
+#define TTY_OVERRUN	4
+
+#endif