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authorDavid Brownell <david-b@pacbell.net>2008-07-04 12:59:26 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-04 13:40:04 -0400
commita01cc6570326c01e70619bf6540fb32139947c33 (patch)
tree810c96598eebc23ca7e53a25b857a9143a17d7d6 /drivers
parent251b97f552b1ad414cc5a9ccc8e4e94503edd5fc (diff)
rtc: rtc_read_alarm() handles wraparound
While 0e36a9a4a788e4e92407774df76c545910810d35 ("rtc: fix readback from /sys/class/rtc/rtc?/wakealarm") made sure that active alarms were never returned with invalid "wildcard" fields (negative), it can still report (wrongly) that the alarm triggers in the past. Example, if it's now 10am, an alarm firing at 5am will be triggered TOMORROW not today. (Which may also be next month or next year...) This updates that alarm handling in three ways: * Handle alarm rollover in the common cases of RTCs that don't support matching on all date fields. * Skip the invalid-field logic when it's not needed. * Minor bugfix ... tm_isdst should be ignored, it's one of the fields Linux doesn't maintain. A warning is emitted for some of the unhandled rollover cases, but the possible combinations are a bit too numerous to handle every bit of potential hardware and firmware braindamage. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Mark Lord <lkml@rtr.ca> Acked-by: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/rtc/interface.c102
1 files changed, 91 insertions, 11 deletions
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 7e3ad4f3b343..58b7336640ff 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -126,12 +126,25 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
126 int err; 126 int err;
127 struct rtc_time before, now; 127 struct rtc_time before, now;
128 int first_time = 1; 128 int first_time = 1;
129 unsigned long t_now, t_alm;
130 enum { none, day, month, year } missing = none;
131 unsigned days;
129 132
130 /* The lower level RTC driver may not be capable of filling 133 /* The lower level RTC driver may return -1 in some fields,
131 * in all fields of the rtc_time struct (eg. rtc-cmos), 134 * creating invalid alarm->time values, for reasons like:
132 * and so might instead return -1 in some fields. 135 *
133 * We deal with that here by grabbing a current RTC timestamp 136 * - The hardware may not be capable of filling them in;
134 * and using values from that for any missing (-1) values. 137 * many alarms match only on time-of-day fields, not
138 * day/month/year calendar data.
139 *
140 * - Some hardware uses illegal values as "wildcard" match
141 * values, which non-Linux firmware (like a BIOS) may try
142 * to set up as e.g. "alarm 15 minutes after each hour".
143 * Linux uses only oneshot alarms.
144 *
145 * When we see that here, we deal with it by using values from
146 * a current RTC timestamp for any missing (-1) values. The
147 * RTC driver prevents "periodic alarm" modes.
135 * 148 *
136 * But this can be racey, because some fields of the RTC timestamp 149 * But this can be racey, because some fields of the RTC timestamp
137 * may have wrapped in the interval since we read the RTC alarm, 150 * may have wrapped in the interval since we read the RTC alarm,
@@ -174,6 +187,10 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
174 if (!alarm->enabled) 187 if (!alarm->enabled)
175 return 0; 188 return 0;
176 189
190 /* full-function RTCs won't have such missing fields */
191 if (rtc_valid_tm(&alarm->time) == 0)
192 return 0;
193
177 /* get the "after" timestamp, to detect wrapped fields */ 194 /* get the "after" timestamp, to detect wrapped fields */
178 err = rtc_read_time(rtc, &now); 195 err = rtc_read_time(rtc, &now);
179 if (err < 0) 196 if (err < 0)
@@ -183,22 +200,85 @@ int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
183 } while ( before.tm_min != now.tm_min 200 } while ( before.tm_min != now.tm_min
184 || before.tm_hour != now.tm_hour 201 || before.tm_hour != now.tm_hour
185 || before.tm_mon != now.tm_mon 202 || before.tm_mon != now.tm_mon
186 || before.tm_year != now.tm_year 203 || before.tm_year != now.tm_year);
187 || before.tm_isdst != now.tm_isdst);
188 204
189 /* Fill in any missing alarm fields using the timestamp */ 205 /* Fill in the missing alarm fields using the timestamp; we
206 * know there's at least one since alarm->time is invalid.
207 */
190 if (alarm->time.tm_sec == -1) 208 if (alarm->time.tm_sec == -1)
191 alarm->time.tm_sec = now.tm_sec; 209 alarm->time.tm_sec = now.tm_sec;
192 if (alarm->time.tm_min == -1) 210 if (alarm->time.tm_min == -1)
193 alarm->time.tm_min = now.tm_min; 211 alarm->time.tm_min = now.tm_min;
194 if (alarm->time.tm_hour == -1) 212 if (alarm->time.tm_hour == -1)
195 alarm->time.tm_hour = now.tm_hour; 213 alarm->time.tm_hour = now.tm_hour;
196 if (alarm->time.tm_mday == -1) 214
215 /* For simplicity, only support date rollover for now */
216 if (alarm->time.tm_mday == -1) {
197 alarm->time.tm_mday = now.tm_mday; 217 alarm->time.tm_mday = now.tm_mday;
198 if (alarm->time.tm_mon == -1) 218 missing = day;
219 }
220 if (alarm->time.tm_mon == -1) {
199 alarm->time.tm_mon = now.tm_mon; 221 alarm->time.tm_mon = now.tm_mon;
200 if (alarm->time.tm_year == -1) 222 if (missing == none)
223 missing = month;
224 }
225 if (alarm->time.tm_year == -1) {
201 alarm->time.tm_year = now.tm_year; 226 alarm->time.tm_year = now.tm_year;
227 if (missing == none)
228 missing = year;
229 }
230
231 /* with luck, no rollover is needed */
232 rtc_tm_to_time(&now, &t_now);
233 rtc_tm_to_time(&alarm->time, &t_alm);
234 if (t_now < t_alm)
235 goto done;
236
237 switch (missing) {
238
239 /* 24 hour rollover ... if it's now 10am Monday, an alarm that
240 * that will trigger at 5am will do so at 5am Tuesday, which
241 * could also be in the next month or year. This is a common
242 * case, especially for PCs.
243 */
244 case day:
245 dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day");
246 t_alm += 24 * 60 * 60;
247 rtc_time_to_tm(t_alm, &alarm->time);
248 break;
249
250 /* Month rollover ... if it's the 31th, an alarm on the 3rd will
251 * be next month. An alarm matching on the 30th, 29th, or 28th
252 * may end up in the month after that! Many newer PCs support
253 * this type of alarm.
254 */
255 case month:
256 dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month");
257 do {
258 if (alarm->time.tm_mon < 11)
259 alarm->time.tm_mon++;
260 else {
261 alarm->time.tm_mon = 0;
262 alarm->time.tm_year++;
263 }
264 days = rtc_month_days(alarm->time.tm_mon,
265 alarm->time.tm_year);
266 } while (days < alarm->time.tm_mday);
267 break;
268
269 /* Year rollover ... easy except for leap years! */
270 case year:
271 dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year");
272 do {
273 alarm->time.tm_year++;
274 } while (!rtc_valid_tm(&alarm->time));
275 break;
276
277 default:
278 dev_warn(&rtc->dev, "alarm rollover not handled\n");
279 }
280
281done:
202 return 0; 282 return 0;
203} 283}
204EXPORT_SYMBOL_GPL(rtc_read_alarm); 284EXPORT_SYMBOL_GPL(rtc_read_alarm);