1biodone(9F) Kernel Functions for Drivers biodone(9F)
2
6 biodone - release buffer after buffer I/O transfer and notify blocked
7 threads
8
10 #include <sys/types.h>
11 #include <sys/buf.h>
12 void biodone(struct buf *bp);
16
19 Architecture independent level 1 (DDI/DKI).
20
22 bp Pointer to a buf(9S) structure.
23
26 The biodone() function notifies blocked processes waiting for the I/O
27 to complete, sets the B_DONE flag in the b_flags field of the buf(9S)
28 structure, and releases the buffer if the I/O is asynchronous.
29 biodone() is called by either the driver interrupt or strategy(9E) rou‐
30 tines when a buffer I/O request is complete.
31 The biodone() function provides the capability to call a completion
34 routine if bp describes a kernel buffer. The address of the routine is
35 specified in the b_iodone field of the buf(9S) structure. If such a
36 routine is specified, biodone() calls it and returns without performing
37 any other actions. Otherwise, it performs the steps above.
38
40 The biodone() function can be called from user, interrupt, or kernel
41 context.
42
44 Generally, the first validation test performed by any block device
45 strategy(9E) routine is a check for an end-of-file (EOF) condition. The
46 strategy(9E) routine is responsible for determining an EOF condition
47 when the device is accessed directly. If a read(2) request is made for
48 one block beyond the limits of the device (line 10), it will report an
49 EOF condition. Otherwise, if the request is outside the limits of the
50 device, the routine will report an error condition. In either case,
51 report the I/O operation as complete (line 27).
52 1 #define RAMDNBLK 1000 /* Number of blocks in RAM disk */
54 2 #define RAMDBSIZ 512 /* Number of bytes per block */
55 3 char ramdblks[RAMDNBLK][RAMDBSIZ]; /* Array containing RAM disk */
56 4
57 5 static int
58 6 ramdstrategy(struct buf *bp)
59 7 {
60 8 daddr_t blkno = bp->b_blkno; /* get block number */
61 9
62 10 if ((blkno < 0) || (blkno >= RAMDNBLK)) {
63 11 /*
64 12 * If requested block is outside RAM disk
65 13 * limits, test for EOF which could result
66 14 * from a direct (physio) request.
67 15 */
68 16 if ((blkno == RAMDNBLK) && (bp->b_flags & B_READ)) {
69 17 /*
70 18 * If read is for block beyond RAM disk
71 19 * limits, mark EOF condition.
72 20 */
73 21 bp->b_resid = bp->b_bcount; /* compute return value */
74 22
75 23 } else { /* I/O attempt is beyond */
76 24 bp->b_error = ENXIO; /* limits of RAM disk */
77 25 bp->b_flags |= B_ERROR; /* return error */
78 26 }
79 27 biodone(bp); /* mark I/O complete (B_DONE) */
80 28 /*
81 29 * Wake any processes awaiting this I/O
82 30 * or release buffer for asynchronous
83 31 * (B_ASYNC) request.
84 32 */
85 33 return (0);
86 34 }
87 ...
88
91 read(2), strategy(9E), biowait(9F), ddi_add_intr(9F), delay(9F), time‐
92 out(9F), untimeout(9F), buf(9S)
93 Writing Device Drivers
96
98 After calling biodone(), bp is no longer available to be referred to by
99 the driver. If the driver makes any reference to bp after calling
100 biodone(), a panic may result.
101
103 Drivers that use the b_iodone field of the buf(9S) structure to specify
104 a substitute completion routine should save the value of b_iodone
105 before changing it, and then restore the old value before calling
106 biodone() to release the buffer.
107SunOS 5.11 16 Jan 2006 biodone(9F)