Re: event sequencing

[Kay Sievers <kay.sievers@vrfy.org>]

On Sat, 2005-02-26 at 12:34 -0500, Jon Smirl wrote:
>On Sat, 26 Feb 2005 14:11:08 +0100, Kay Sievers <kay.sievers@vrfy.org> wrote:
>> Stuff like HAL heavily depends on that as it needs to get the initial
>> state of all devices at startup to present this to applications. But if
>> there is any other way to get that without sysfs, it would work too,
>> sure.
>
>I do have somewhat of a race issue. 
>
>1) receive hardware interrupt of monitor change
>2) empty the list of valid modes in sysfs
>3) generate hotplug event to run userspace helper
>4) userspace helper sets in new mode list
>5) driver generates HAL event
>
>X could have picked a mode from the modelist before #1
>Then tried to set it between #1 and #4
>In this case X will get an error about invalid mode
>That should cause a popup that tells the user to try again
>while that popup is up the HAL event occurs indicating a new mode list
>is available
>This needs to be sorted out so that the contents of the mode selection
>dialog update

Yeah, this happens with other devices too and I don't see it as a big
problem as long as is fails and the caller get an error back.

>There need to be two events:
>MODELIST_CHANGE
>MODE_CHANGE
>
>MODE_CHANGE occurs if you are in an xterm and set a new mode via the
>command line. X needs to know in order to fix the display.

Are the list and the current state available as device attributes in
sysfs? So you may just send a KOBJ_CHANGE event for that specific
attributes with the kobject_uevent() which can have an attribute passed
down which is appended to the devpath of the device.

Kay



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