arm: tegra: cardhu: remove NVSD debug message
[linux-2.6.git] / fs / fifo.c
1 /*
2  *  linux/fs/fifo.c
3  *
4  *  written by Paul H. Hargrove
5  *
6  *  Fixes:
7  *      10-06-1999, AV: fixed OOM handling in fifo_open(), moved
8  *                      initialization there, switched to external
9  *                      allocation of pipe_inode_info.
10  */
11
12 #include <linux/mm.h>
13 #include <linux/fs.h>
14 #include <linux/sched.h>
15 #include <linux/pipe_fs_i.h>
16
17 static void wait_for_partner(struct inode* inode, unsigned int *cnt)
18 {
19         int cur = *cnt; 
20
21         while (cur == *cnt) {
22                 pipe_wait(inode->i_pipe);
23                 if (signal_pending(current))
24                         break;
25         }
26 }
27
28 static void wake_up_partner(struct inode* inode)
29 {
30         wake_up_interruptible(&inode->i_pipe->wait);
31 }
32
33 static int fifo_open(struct inode *inode, struct file *filp)
34 {
35         struct pipe_inode_info *pipe;
36         int ret;
37
38         mutex_lock(&inode->i_mutex);
39         pipe = inode->i_pipe;
40         if (!pipe) {
41                 ret = -ENOMEM;
42                 pipe = alloc_pipe_info(inode);
43                 if (!pipe)
44                         goto err_nocleanup;
45                 inode->i_pipe = pipe;
46         }
47         filp->f_version = 0;
48
49         /* We can only do regular read/write on fifos */
50         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
51
52         switch (filp->f_mode) {
53         case FMODE_READ:
54         /*
55          *  O_RDONLY
56          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
57          *  opened, even when there is no process writing the FIFO.
58          */
59                 filp->f_op = &read_pipefifo_fops;
60                 pipe->r_counter++;
61                 if (pipe->readers++ == 0)
62                         wake_up_partner(inode);
63
64                 if (!pipe->writers) {
65                         if ((filp->f_flags & O_NONBLOCK)) {
66                                 /* suppress POLLHUP until we have
67                                  * seen a writer */
68                                 filp->f_version = pipe->w_counter;
69                         } else {
70                                 wait_for_partner(inode, &pipe->w_counter);
71                                 if(signal_pending(current))
72                                         goto err_rd;
73                         }
74                 }
75                 break;
76         
77         case FMODE_WRITE:
78         /*
79          *  O_WRONLY
80          *  POSIX.1 says that O_NONBLOCK means return -1 with
81          *  errno=ENXIO when there is no process reading the FIFO.
82          */
83                 ret = -ENXIO;
84                 if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
85                         goto err;
86
87                 filp->f_op = &write_pipefifo_fops;
88                 pipe->w_counter++;
89                 if (!pipe->writers++)
90                         wake_up_partner(inode);
91
92                 if (!pipe->readers) {
93                         wait_for_partner(inode, &pipe->r_counter);
94                         if (signal_pending(current))
95                                 goto err_wr;
96                 }
97                 break;
98         
99         case FMODE_READ | FMODE_WRITE:
100         /*
101          *  O_RDWR
102          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
103          *  This implementation will NEVER block on a O_RDWR open, since
104          *  the process can at least talk to itself.
105          */
106                 filp->f_op = &rdwr_pipefifo_fops;
107
108                 pipe->readers++;
109                 pipe->writers++;
110                 pipe->r_counter++;
111                 pipe->w_counter++;
112                 if (pipe->readers == 1 || pipe->writers == 1)
113                         wake_up_partner(inode);
114                 break;
115
116         default:
117                 ret = -EINVAL;
118                 goto err;
119         }
120
121         /* Ok! */
122         mutex_unlock(&inode->i_mutex);
123         return 0;
124
125 err_rd:
126         if (!--pipe->readers)
127                 wake_up_interruptible(&pipe->wait);
128         ret = -ERESTARTSYS;
129         goto err;
130
131 err_wr:
132         if (!--pipe->writers)
133                 wake_up_interruptible(&pipe->wait);
134         ret = -ERESTARTSYS;
135         goto err;
136
137 err:
138         if (!pipe->readers && !pipe->writers)
139                 free_pipe_info(inode);
140
141 err_nocleanup:
142         mutex_unlock(&inode->i_mutex);
143         return ret;
144 }
145
146 /*
147  * Dummy default file-operations: the only thing this does
148  * is contain the open that then fills in the correct operations
149  * depending on the access mode of the file...
150  */
151 const struct file_operations def_fifo_fops = {
152         .open           = fifo_open,    /* will set read_ or write_pipefifo_fops */
153         .llseek         = noop_llseek,
154 };