David Zeuthen wrote:
On Wed, 2008-04-02 at 12:57 -0400, Doug Goldstein wrote:
David Zeuthen wrote:
On Wed, 2008-04-02 at 10:52 +0100, Sam Morris wrote:
Attached is a patch to fix the problem with wakeups. This patch does
CDROM_MEDIA_CHANGED first, and if it reports true, then checks to make
sure the drive is closed and then that the drive is not lying. This
causes the number of wakeups from HAL to go to zero. It also has the
side effect of issuing an extra ioctl(2) when the drive tray is open,
which is harmless since the drive tray should be closed most of the
time.
So if I understand this correctly, what this patch does is to reduce the
number of wakeups only when the drive door is open?
David
No. Other way around. It'll increase the number of wakeups when the
drive door is opened and decrease them when it's closed.
Hmm. I'm confused how it can bring the wakeups to zero as is claimed
upthread. Surely the kernel won't know if media is changed unless it
asks the drive [1]. And the kernel won't do this by itself since it's a
policy decision to do so. Or to put it in another way: To detect media
changes the drive _will_ need to be polled from user space - SATA AN
wasn't invented for nothing.
Now I could be wrong (I'm not too well versed in hardware specs and
driver bits). I was under the impression that MMC-2 ATAPI provides for a
Media Status Notification. Which is a polled condition. However, the
device should emit an Unit Attention Condition when a disc *may* have
been removed. Which basically means, the device should emit a notice
when the drive door opens and closes to tell you that the media may have
changed.
As the bug report explains now, HAL is checking for the drive door to be
closed. Instead of relying on the Unit Attention Condition notice.
His patch would bring hal-addon-storage's wakeups down since it would
offload more work on the kernel where the wakeups would occur.
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