On 10/10/2010, at 22.55, Alexander Motin wrote: > Pawel Jakub Dawidek wrote: >> On Thu, Sep 30, 2010 at 08:46:11PM +0300, Alexander Motin wrote: >>> Andriy Gapon wrote: >>>> on 30/09/2010 01:28 Matthew Jacob said the following: >>>>> If something like that was in place, I assure you that things would start >>>>> to use >>>>> it very quickly. >>>> I am not sure about this. >>>> Because, e.g. I don't see an easy way to know that media is changed in >>>> scsi_cd >>>> driver. That is, without polling. I don't consider polling to be an easy >>>> way for >>>> a number of reasons. >>> SATA specification defines concept of Asynchronous Notification. It is >>> already used by port multipliers to report about PHY events. It is also >>> supposed to be used by CD drives to report media change. I haven't seen >>> such devices yet, but hope they may appear sometimes. >>> >>> And even without AN support it would be nice to implement proper >>> handling for SCSI "UA - media changed" errors within CAM. It still won't >>> be perfect without using polling, but probably still something. >> >> I'd like to know the original reason why CD device is represented by >> GEOM provider and not CD media. For my naive thinking CD media should be >> GEOM provider that we taste once the media is inserted and orphan once >> the media is removed. I don't see any reasons for CD device to be useful >> GEOM provider, but maybe I'm overlooking something. >> >> Poul-Henning or Soren, do you remember who made and why this design choice? > > SCSI drivers receive no notification on media insertion. Somebody should > poll device. At this moment it is handled by consumers. Indeed not sure > it is the best idea. If we want driver to bother with this polling - we > may do as you propose. Actually in sdhci(4) driver I am doing this way - > mmcsdX device appears when card inserted and disappears on removal. > > I think first thing that may brake if there will be no cdX device - > loading the media with some commands. Also it may be non-intuitive that > drive is present, but disk is not registered in GEOM.
Think burning data on empty media. -Søren "Any sufficiently advanced technology is indistinguishable from magic." -- _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "[email protected]"
