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authorLukas Prediger2021-09-14 00:09:42 +0100
committerJens Axboe2021-09-14 20:05:26 -0600
commit67f1e027c27054e641584655020a417eaac9cb3a (patch)
treecd436e8c697009cc6def17e4b77cd28503029ac3 /Documentation/userspace-api
parent316346243be6df12799c0b64b788e06bad97c30b (diff)
drivers/cdrom: improved ioctl for media change detection
The current implementation of the CDROM_MEDIA_CHANGED ioctl relies on global state, meaning that only one process can detect a disc change while the ioctl call will return 0 for other calling processes afterwards (see bug 213267). This introduces a new cdrom ioctl, CDROM_TIMED_MEDIA_CHANGE, that works by maintaining a timestamp of the last detected disc change instead of a boolean flag: Processes calling this ioctl command can provide a timestamp of the last disc change known to them and receive an indication whether the disc was changed since then and the updated timestamp. I considered fixing the buggy behavior in the original CDROM_MEDIA_CHANGED ioctl but that would require maintaining state for each calling process in the kernel, which seems like a worse solution than introducing this new ioctl. Signed-off-by: Lukas Prediger <lumip@lumip.de> Link: https://lore.kernel.org/all/20210912191207.74449-1-lumip@lumip.de Signed-off-by: Phillip Potter <phil@philpotter.co.uk> Link: https://lore.kernel.org/r/20210913230942.1188-1-phil@philpotter.co.uk Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'Documentation/userspace-api')
-rw-r--r--Documentation/userspace-api/ioctl/cdrom.rst3
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/userspace-api/ioctl/cdrom.rst b/Documentation/userspace-api/ioctl/cdrom.rst
index 3b4c0506de46..bac5bbf93ca0 100644
--- a/Documentation/userspace-api/ioctl/cdrom.rst
+++ b/Documentation/userspace-api/ioctl/cdrom.rst
@@ -54,6 +54,9 @@ are as follows:
CDROM_SELECT_SPEED Set the CD-ROM speed
CDROM_SELECT_DISC Select disc (for juke-boxes)
CDROM_MEDIA_CHANGED Check is media changed
+ CDROM_TIMED_MEDIA_CHANGE Check if media changed
+ since given time
+ (struct cdrom_timed_media_change_info)
CDROM_DRIVE_STATUS Get tray position, etc.
CDROM_DISC_STATUS Get disc type, etc.
CDROM_CHANGER_NSLOTS Get number of slots