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. However it's
problematic in the fact that Linux does not do per-process
CDROM_MEDIA_CHANGED. If another app reads that, then HAL will never know
that the media changed.
Right now HAL always checks to see if the drive door and then assumes
there is media in the drive.
The downside to the patch is that it relies on CDROM_MEDIA_CHANGED not
being touched by another app. So with the patch HAL, will cause less
interrupts but will miss media changes in some situations..
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