include/linux/tty_buffer.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_TTY_BUFFER_H
   3 #define _LINUX_TTY_BUFFER_H
   4
   5 #include <linux/atomic.h>
   6 #include <linux/llist.h>
   7 #include <linux/mutex.h>
   8 #include <linux/workqueue.h>
   9
  10 struct tty_buffer {
  11         union {
  12                 struct tty_buffer *next;
  13                 struct llist_node free;
  14         };
  15         unsigned int used;
  16         unsigned int size;
  17         unsigned int commit;
  18         unsigned int lookahead;         /* Lazy update on recv, can become less than "read" */
  19         unsigned int read;
  20         bool flags;
  21         /* Data points here */
  22         u8 data[] __aligned(sizeof(unsigned long));
  23 };
  24
  25 static inline u8 *char_buf_ptr(struct tty_buffer *b, unsigned int ofs)
  26 {
  27         return b->data + ofs;
  28 }
  29
  30 static inline u8 *flag_buf_ptr(struct tty_buffer *b, unsigned int ofs)
  31 {
  32         return char_buf_ptr(b, ofs) + b->size;
  33 }
  34
  35 struct tty_bufhead {
  36         struct tty_buffer *head;        /* Queue head */
  37         struct work_struct work;
  38         struct mutex       lock;
  39         atomic_t           priority;
  40         struct tty_buffer sentinel;
  41         struct llist_head free;         /* Free queue head */
  42         atomic_t           mem_used;    /* In-use buffers excluding free list */
  43         int                mem_limit;
  44         struct tty_buffer *tail;        /* Active buffer */
  45 };
  46
  47 /*
  48  * When a break, frame error, or parity error happens, these codes are
  49  * stuffed into the flags buffer.
  50  */
  51 #define TTY_NORMAL      0
  52 #define TTY_BREAK       1
  53 #define TTY_FRAME       2
  54 #define TTY_PARITY      3
  55 #define TTY_OVERRUN     4
  56
  57 #endif