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authorJoe Peterson <joe@skyrush.com>2008-07-25 04:46:47 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-25 13:53:34 -0400
commitb271e067c896ad4082b15e96077675d08db40625 (patch)
tree1837d1c988226116e277c4f71b7f57aed5a7df05 /fs/fat/misc.c
parente8938a62a85d1f487e02c3b01955b47c9598f6d2 (diff)
fatfs: add UTC timestamp option
Provide a new mount option ("tz=UTC") for DOS (vfat/msdos) filesystems, allowing timestamps to be in coordinated universal time (UTC) rather than local time in applications where doing this is advantageous. In particular, portable devices that use fat/vfat (such as digital cameras) can benefit from using UTC in their internal clocks, thus avoiding daylight saving time errors and general time ambiguity issues. The user of the device does not have to worry about changing the time when moving from place or when daylight saving changes. The new mount option, when set, disables the counter-adjustment that Linux currently makes to FAT timestamp info in anticipation of the normal userspace time zone correction. When used in this new mode, all daylight saving time and time zone handling is done in userspace as is normal for many other filesystems (like ext3). The default mode, which remains unchanged, is still appropriate when mounting volumes written in Windows (because of its use of local time). I originally based this patch on one submitted last year by Paul Collins, but I updated it to work with current source and changed variable/option naming. Ogawa Hirofumi (who maintains these filesystems) and I discussed this patch at length on lkml, and he suggested using the option name in the attached version of the patch. Barry Bouwsma pointed out a good addition to the patch as well. Signed-off-by: Joe Peterson <joe@skyrush.com> Signed-off-by: Paul Collins <paul@ondioline.org> Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Barry Bouwsma <free_beer_for_all@yahoo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/fat/misc.c')
-rw-r--r--fs/fat/misc.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index 61f23511eacf..79fb98ad36d4 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -142,7 +142,7 @@ static int day_n[] = {
142}; 142};
143 143
144/* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */ 144/* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
145int date_dos2unix(unsigned short time, unsigned short date) 145int date_dos2unix(unsigned short time, unsigned short date, int tz_utc)
146{ 146{
147 int month, year, secs; 147 int month, year, secs;
148 148
@@ -156,16 +156,18 @@ int date_dos2unix(unsigned short time, unsigned short date)
156 ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 && 156 ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
157 month < 2 ? 1 : 0)+3653); 157 month < 2 ? 1 : 0)+3653);
158 /* days since 1.1.70 plus 80's leap day */ 158 /* days since 1.1.70 plus 80's leap day */
159 secs += sys_tz.tz_minuteswest*60; 159 if (!tz_utc)
160 secs += sys_tz.tz_minuteswest*60;
160 return secs; 161 return secs;
161} 162}
162 163
163/* Convert linear UNIX date to a MS-DOS time/date pair. */ 164/* Convert linear UNIX date to a MS-DOS time/date pair. */
164void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date) 165void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date, int tz_utc)
165{ 166{
166 int day, year, nl_day, month; 167 int day, year, nl_day, month;
167 168
168 unix_date -= sys_tz.tz_minuteswest*60; 169 if (!tz_utc)
170 unix_date -= sys_tz.tz_minuteswest*60;
169 171
170 /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */ 172 /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
171 if (unix_date < 315532800) 173 if (unix_date < 315532800)