On Mon, 2007-10-29 at 12:24 -0400, Jeff Garzik wrote: > James Bottomley wrote: > > Ah, OK; I haven't communicated what we need very clearly. We need a way > > to see if the event is supported by the device, as well as a way to turn > > it off. For some of the events (possibly not the SATA AN one, since I > > know all SATA devices will be well behaved) there's going to be a need > > to deal with berserk or broken devices that become trigger happy, so > > turning off the event will be a useful (and possibly essential) way of > > coping. > > > That's possible with the presented interface[1]: > > # see if event is supported > cat $path/evt_media_change > > # turn off event to deal with broken/beserk devices > echo 0 > $path/evt_media_change > > Some sillyhead can always do > > echo 1 > $path/evt_some_event_my_device_does_not_support > > but that will be obviously be a no-op because their device simply will > not send such events. > > Granted ls(1) is no longer a method for viewing supported-at-boot-time > list of events -- ls(1) in the presented interface lists what events the > _kernel_ supports, and cat(1) is used to discover which events are > actually enabled. > > I think that is the only difference between our two positions: [if I > understand you correctly] you want ls(1) to be able to list the device's > supported events. However, I feel that is inconsistent: for your > proposal, userspace must perform two checks in order to determine a > feature's availability: 1) does the file exist? 2) is the file context > non-zero? Yes, I agree ... however, open file is one op for the user -ENXIO means device doesn't support the event; value indicates whether the event is currently triggering. I just would rather we use the file exists if device supports event, because it's consistent with all the rest of our SCSI interfaces. > Regards, > > Jeff > > > [1] modulo my comment from the original email in this thread: > > * I was slack and did not bother to implement the 'set' operation > > for the attributes. This can easily be done at a later time in a > > separate patch. James - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
