Peter M. Groen / tty0tty

Commit 0fdf7a3ea381e0d12a46883e97af808d959255e9

Authored by Craig McQueen
1 parent df2832d8

Enable some data flow control according to the unread data buffer of the paired port.

Inline Side-by-side
Showing 1 changed file with 32 additions and 3 deletions
module/tty0tty.c
  View file @0fdf7a3
... ... @@ -72,6 +72,8 @@ MODULE_LICENSE("GPL");
72 72 #define MSR_DSR 0x40
73 73 #define MSR_RI 0x80
74 74  
  75 +#define WRITE_ROOM_MAX 64
  76 +
75 77 struct tty0tty_serial {
76 78 struct tty_struct *tty; /* pointer to the tty for this device */
77 79 int open_count; /* number of times this port has been opened */
... ... @@ -89,6 +91,8 @@ struct tty0tty_serial {
89 91  
90 92 static struct tty0tty_serial *tty0tty_table[TINY_TTY_MINORS]; /* initially all NULL */
91 93  
  94 +/* Function prototypes */
  95 +static int tty0tty_write_room(struct tty_struct *tty);
92 96  
93 97 static inline void null_modem_signal_copy(struct tty0tty_serial * tty_to, const struct tty0tty_serial * tty_from)
94 98 {
... ... @@ -197,6 +201,12 @@ static int tty0tty_write(struct tty_struct *tty, const unsigned char *buffer, in
197 201 int retval = -EINVAL;
198 202 struct tty_struct *ttyx = NULL;
199 203 int paired_index;
  204 + int room = 0;
  205 +
  206 + room = tty0tty_write_room(tty);
  207 + if (room < 0)
  208 + /* error case */
  209 + return room;
200 210  
201 211 if (!tty0tty)
202 212 return -ENODEV;
... ... @@ -214,12 +224,14 @@ static int tty0tty_write(struct tty_struct *tty, const unsigned char *buffer, in
214 224  
215 225 // tty->low_latency=1;
216 226  
  227 + if (count > room)
  228 + count = room;
217 229 if(ttyx != NULL)
218 230 {
219 231 tty_insert_flip_string(ttyx, buffer, count);
220 232 tty_flip_buffer_push(ttyx);
221   - retval=count;
222 233 }
  234 + retval=count;
223 235  
224 236 exit:
225 237 up(&tty0tty->sem);
... ... @@ -229,20 +241,37 @@ exit:
229 241 static int tty0tty_write_room(struct tty_struct *tty)
230 242 {
231 243 struct tty0tty_serial *tty0tty = tty->driver_data;
  244 + struct tty0tty_serial *tty0tty_paired = NULL;
  245 + int index;
  246 + int paired_index;
232 247 int room = -EINVAL;
233 248  
234 249 if (!tty0tty)
235 250 return -ENODEV;
236 251  
237 252 down(&tty0tty->sem);
238   -
  253 +
239 254 if (!tty0tty->open_count) {
240 255 /* port was not opened */
241 256 goto exit;
242 257 }
243 258  
  259 + /* get the serial object associated with this tty pointer */
  260 + index = tty->index;
  261 + paired_index = PAIRED_INDEX(index);
  262 + tty0tty_paired = tty0tty_table[paired_index];
  263 + if (tty0tty_paired == NULL || tty0tty_paired->open_count == 0) {
  264 + /* Paired port is not open */
  265 + /* Effectively dump all written bytes */
  266 + room = WRITE_ROOM_MAX;
  267 + goto exit;
  268 + }
  269 +
244 270 /* calculate how much room is left in the device */
245   - room = 255;
  271 + room = WRITE_ROOM_MAX - tty0tty_paired->tty->read_cnt;
  272 + if (room < 0) {
  273 + room = 0;
  274 + }
246 275  
247 276 exit:
248 277 up(&tty0tty->sem);
... ...