staging: iio: ring_sw: Fix incorrect test on successful read of last value, causes...
[linux-2.6.git] / drivers / staging / iio / ring_sw.c
1 /* The industrial I/O simple minimally locked ring buffer.
2  *
3  * Copyright (c) 2008 Jonathan Cameron
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 as published by
7  * the Free Software Foundation.
8  */
9
10 #include <linux/slab.h>
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/device.h>
14 #include <linux/workqueue.h>
15 #include "ring_sw.h"
16
17 static inline int __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
18                                             int bytes_per_datum, int length)
19 {
20         if ((length == 0) || (bytes_per_datum == 0))
21                 return -EINVAL;
22
23         __iio_init_ring_buffer(&ring->buf, bytes_per_datum, length);
24         spin_lock_init(&ring->use_lock);
25         ring->data = kmalloc(length*ring->buf.bpd, GFP_KERNEL);
26         ring->read_p = 0;
27         ring->write_p = 0;
28         ring->last_written_p = 0;
29         ring->half_p = 0;
30         return ring->data ? 0 : -ENOMEM;
31 }
32
33 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
34 {
35         kfree(ring->data);
36 }
37
38 void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
39 {
40         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
41         spin_lock(&ring->use_lock);
42         ring->use_count++;
43         spin_unlock(&ring->use_lock);
44 }
45 EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
46
47 void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
48 {
49         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
50         spin_lock(&ring->use_lock);
51         ring->use_count--;
52         spin_unlock(&ring->use_lock);
53 }
54 EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
55
56
57 /* Ring buffer related functionality */
58 /* Store to ring is typically called in the bh of a data ready interrupt handler
59  * in the device driver */
60 /* Lock always held if their is a chance this may be called */
61 /* Only one of these per ring may run concurrently - enforced by drivers */
62 int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
63                          unsigned char *data,
64                          s64 timestamp)
65 {
66         int ret = 0;
67         int code;
68         unsigned char *temp_ptr, *change_test_ptr;
69
70         /* initial store */
71         if (unlikely(ring->write_p == 0)) {
72                 ring->write_p = ring->data;
73                 /* Doesn't actually matter if this is out of the set
74                  * as long as the read pointer is valid before this
75                  * passes it - guaranteed as set later in this function.
76                  */
77                 ring->half_p = ring->data - ring->buf.length*ring->buf.bpd/2;
78         }
79         /* Copy data to where ever the current write pointer says */
80         memcpy(ring->write_p, data, ring->buf.bpd);
81         barrier();
82         /* Update the pointer used to get most recent value.
83          * Always valid as either points to latest or second latest value.
84          * Before this runs it is null and read attempts fail with -EAGAIN.
85          */
86         ring->last_written_p = ring->write_p;
87         barrier();
88         /* temp_ptr used to ensure we never have an invalid pointer
89          * it may be slightly lagging, but never invalid
90          */
91         temp_ptr = ring->write_p + ring->buf.bpd;
92         /* End of ring, back to the beginning */
93         if (temp_ptr == ring->data + ring->buf.length*ring->buf.bpd)
94                 temp_ptr = ring->data;
95         /* Update the write pointer
96          * always valid as long as this is the only function able to write.
97          * Care needed with smp systems to ensure more than one ring fill
98          * is never scheduled.
99          */
100         ring->write_p = temp_ptr;
101
102         if (ring->read_p == 0)
103                 ring->read_p = ring->data;
104         /* Buffer full - move the read pointer and create / escalate
105          * ring event */
106         /* Tricky case - if the read pointer moves before we adjust it.
107          * Handle by not pushing if it has moved - may result in occasional
108          * unnecessary buffer full events when it wasn't quite true.
109          */
110         else if (ring->write_p == ring->read_p) {
111                 change_test_ptr = ring->read_p;
112                 temp_ptr = change_test_ptr + ring->buf.bpd;
113                 if (temp_ptr
114                     == ring->data + ring->buf.length*ring->buf.bpd) {
115                         temp_ptr = ring->data;
116                 }
117                 /* We are moving pointer on one because the ring is full.  Any
118                  * change to the read pointer will be this or greater.
119                  */
120                 if (change_test_ptr == ring->read_p)
121                         ring->read_p = temp_ptr;
122
123                 spin_lock(&ring->buf.shared_ev_pointer.lock);
124
125                 ret = iio_push_or_escallate_ring_event(&ring->buf,
126                                                        IIO_EVENT_CODE_RING_100_FULL,
127                                                        timestamp);
128                 spin_unlock(&ring->buf.shared_ev_pointer.lock);
129                 if (ret)
130                         goto error_ret;
131         }
132         /* investigate if our event barrier has been passed */
133         /* There are definite 'issues' with this and chances of
134          * simultaneous read */
135         /* Also need to use loop count to ensure this only happens once */
136         ring->half_p += ring->buf.bpd;
137         if (ring->half_p == ring->data + ring->buf.length*ring->buf.bpd)
138                 ring->half_p = ring->data;
139         if (ring->half_p == ring->read_p) {
140                 spin_lock(&ring->buf.shared_ev_pointer.lock);
141                 code = IIO_EVENT_CODE_RING_50_FULL;
142                 ret = __iio_push_event(&ring->buf.ev_int,
143                                        code,
144                                        timestamp,
145                                        &ring->buf.shared_ev_pointer);
146                 spin_unlock(&ring->buf.shared_ev_pointer.lock);
147         }
148 error_ret:
149         return ret;
150 }
151
152 int iio_rip_sw_rb(struct iio_ring_buffer *r,
153                   size_t count, u8 **data, int *dead_offset)
154 {
155         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
156
157         u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
158         int ret, max_copied;
159         int bytes_to_rip;
160
161         /* A userspace program has probably made an error if it tries to
162          *  read something that is not a whole number of bpds.
163          * Return an error.
164          */
165         if (count % ring->buf.bpd) {
166                 ret = -EINVAL;
167                 printk(KERN_INFO "Ring buffer read request not whole number of"
168                        "samples: Request bytes %zd, Current bpd %d\n",
169                        count, ring->buf.bpd);
170                 goto error_ret;
171         }
172         /* Limit size to whole of ring buffer */
173         bytes_to_rip = min((size_t)(ring->buf.bpd*ring->buf.length), count);
174
175         *data = kmalloc(bytes_to_rip, GFP_KERNEL);
176         if (*data == NULL) {
177                 ret = -ENOMEM;
178                 goto error_ret;
179         }
180
181         /* build local copy */
182         initial_read_p = ring->read_p;
183         if (unlikely(initial_read_p == 0)) { /* No data here as yet */
184                 ret = 0;
185                 goto error_free_data_cpy;
186         }
187
188         initial_write_p = ring->write_p;
189
190         /* Need a consistent pair */
191         while ((initial_read_p != ring->read_p)
192                || (initial_write_p != ring->write_p)) {
193                 initial_read_p = ring->read_p;
194                 initial_write_p = ring->write_p;
195         }
196         if (initial_write_p == initial_read_p) {
197                 /* No new data available.*/
198                 ret = 0;
199                 goto error_free_data_cpy;
200         }
201
202         if (initial_write_p >= initial_read_p + bytes_to_rip) {
203                 /* write_p is greater than necessary, all is easy */
204                 max_copied = bytes_to_rip;
205                 memcpy(*data, initial_read_p, max_copied);
206                 end_read_p = initial_read_p + max_copied;
207         } else if (initial_write_p > initial_read_p) {
208                 /*not enough data to cpy */
209                 max_copied = initial_write_p - initial_read_p;
210                 memcpy(*data, initial_read_p, max_copied);
211                 end_read_p = initial_write_p;
212         } else {
213                 /* going through 'end' of ring buffer */
214                 max_copied = ring->data
215                         + ring->buf.length*ring->buf.bpd - initial_read_p;
216                 memcpy(*data, initial_read_p, max_copied);
217                 /* possible we are done if we align precisely with end */
218                 if (max_copied == bytes_to_rip)
219                         end_read_p = ring->data;
220                 else if (initial_write_p
221                          > ring->data + bytes_to_rip - max_copied) {
222                         /* enough data to finish */
223                         memcpy(*data + max_copied, ring->data,
224                                bytes_to_rip - max_copied);
225                         max_copied = bytes_to_rip;
226                         end_read_p = ring->data + (bytes_to_rip - max_copied);
227                 } else {  /* not enough data */
228                         memcpy(*data + max_copied, ring->data,
229                                initial_write_p - ring->data);
230                         max_copied += initial_write_p - ring->data;
231                         end_read_p = initial_write_p;
232                 }
233         }
234         /* Now to verify which section was cleanly copied - i.e. how far
235          * read pointer has been pushed */
236         current_read_p = ring->read_p;
237
238         if (initial_read_p <= current_read_p)
239                 *dead_offset = current_read_p - initial_read_p;
240         else
241                 *dead_offset = ring->buf.length*ring->buf.bpd
242                         - (initial_read_p - current_read_p);
243
244         /* possible issue if the initial write has been lapped or indeed
245          * the point we were reading to has been passed */
246         /* No valid data read.
247          * In this case the read pointer is already correct having been
248          * pushed further than we would look. */
249         if (max_copied - *dead_offset < 0) {
250                 ret = 0;
251                 goto error_free_data_cpy;
252         }
253
254         /* setup the next read position */
255         /* Beware, this may fail due to concurrency fun and games.
256          *  Possible that sufficient fill commands have run to push the read
257          * pointer past where we would be after the rip. If this occurs, leave
258          * it be.
259          */
260         /* Tricky - deal with loops */
261
262         while (ring->read_p != end_read_p)
263                 ring->read_p = end_read_p;
264
265         return max_copied - *dead_offset;
266
267 error_free_data_cpy:
268         kfree(*data);
269 error_ret:
270         return ret;
271 }
272 EXPORT_SYMBOL(iio_rip_sw_rb);
273
274 int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
275 {
276         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
277         return iio_store_to_sw_ring(ring, data, timestamp);
278 }
279 EXPORT_SYMBOL(iio_store_to_sw_rb);
280
281 int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
282                                unsigned char *data)
283 {
284         unsigned char *last_written_p_copy;
285
286         iio_mark_sw_rb_in_use(&ring->buf);
287 again:
288         barrier();
289         last_written_p_copy = ring->last_written_p;
290         barrier(); /*unnessecary? */
291         /* Check there is anything here */
292         if (last_written_p_copy == 0)
293                 return -EAGAIN;
294         memcpy(data, last_written_p_copy, ring->buf.bpd);
295
296         if (unlikely(ring->last_written_p != last_written_p_copy))
297                 goto again;
298
299         iio_unmark_sw_rb_in_use(&ring->buf);
300         return 0;
301 }
302
303 int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
304                              unsigned char *data)
305 {
306         return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
307 }
308 EXPORT_SYMBOL(iio_read_last_from_sw_rb);
309
310 int iio_request_update_sw_rb(struct iio_ring_buffer *r)
311 {
312         int ret = 0;
313         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
314
315         spin_lock(&ring->use_lock);
316         if (!ring->update_needed)
317                 goto error_ret;
318         if (ring->use_count) {
319                 ret = -EAGAIN;
320                 goto error_ret;
321         }
322         __iio_free_sw_ring_buffer(ring);
323         ret = __iio_init_sw_ring_buffer(ring, ring->buf.bpd, ring->buf.length);
324 error_ret:
325         spin_unlock(&ring->use_lock);
326         return ret;
327 }
328 EXPORT_SYMBOL(iio_request_update_sw_rb);
329
330 int iio_get_bpd_sw_rb(struct iio_ring_buffer *r)
331 {
332         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
333         return ring->buf.bpd;
334 }
335 EXPORT_SYMBOL(iio_get_bpd_sw_rb);
336
337 int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd)
338 {
339         if (r->bpd != bpd) {
340                 r->bpd = bpd;
341                 if (r->access.mark_param_change)
342                         r->access.mark_param_change(r);
343         }
344         return 0;
345 }
346 EXPORT_SYMBOL(iio_set_bpd_sw_rb);
347
348 int iio_get_length_sw_rb(struct iio_ring_buffer *r)
349 {
350         return r->length;
351 }
352 EXPORT_SYMBOL(iio_get_length_sw_rb);
353
354 int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
355 {
356         if (r->length != length) {
357                 r->length = length;
358                 if (r->access.mark_param_change)
359                         r->access.mark_param_change(r);
360         }
361         return 0;
362 }
363 EXPORT_SYMBOL(iio_set_length_sw_rb);
364
365 int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
366 {
367         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
368         ring->update_needed = true;
369         return 0;
370 }
371 EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
372
373 static void iio_sw_rb_release(struct device *dev)
374 {
375         struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
376         kfree(iio_to_sw_ring(r));
377 }
378
379 static IIO_RING_ENABLE_ATTR;
380 static IIO_RING_BPS_ATTR;
381 static IIO_RING_LENGTH_ATTR;
382
383 /* Standard set of ring buffer attributes */
384 static struct attribute *iio_ring_attributes[] = {
385         &dev_attr_length.attr,
386         &dev_attr_bps.attr,
387         &dev_attr_ring_enable.attr,
388         NULL,
389 };
390
391 static struct attribute_group iio_ring_attribute_group = {
392         .attrs = iio_ring_attributes,
393 };
394
395 static const struct attribute_group *iio_ring_attribute_groups[] = {
396         &iio_ring_attribute_group,
397         NULL
398 };
399
400 static struct device_type iio_sw_ring_type = {
401         .release = iio_sw_rb_release,
402         .groups = iio_ring_attribute_groups,
403 };
404
405 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
406 {
407         struct iio_ring_buffer *buf;
408         struct iio_sw_ring_buffer *ring;
409
410         ring = kzalloc(sizeof *ring, GFP_KERNEL);
411         if (!ring)
412                 return 0;
413         buf = &ring->buf;
414
415         iio_ring_buffer_init(buf, indio_dev);
416         buf->dev.type = &iio_sw_ring_type;
417         device_initialize(&buf->dev);
418         buf->dev.parent = &indio_dev->dev;
419         buf->dev.class = &iio_class;
420         dev_set_drvdata(&buf->dev, (void *)buf);
421
422         return buf;
423 }
424 EXPORT_SYMBOL(iio_sw_rb_allocate);
425
426 void iio_sw_rb_free(struct iio_ring_buffer *r)
427 {
428         if (r)
429                 iio_put_ring_buffer(r);
430 }
431 EXPORT_SYMBOL(iio_sw_rb_free);
432 MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
433 MODULE_LICENSE("GPL");