Linus, > Can we place just make the rule be that new mode pages are opt-in, and > *NOT* this kind of broken "opt-out several months later when we > noticed that it inevitably caused problems"? The specific problem with mode pages is that there is no way to know whether a given page is supported without asking for it. Whereas for most of the other things we query at discovery time, the device provides a list of supported pages we can consult before we attempt to query the page itself. > Because if it isn't some mode page that we have already used for > years, it clearly isn't *that* important. [...] > That should give people a big heads up that "maybe this thing isn't > very common or commonly known about"? It is a new feature in SCSI spearheaded by the Android folks. That's why there isn't a lot of information available about it elsewhere. I am super picky about having good heuristics for when we should attempt to query a device for new protocol capabilities. In this case we lacked a reliable indicator that the feature was supported. And since there are non-UFS devices being implemented which support it too, restricting the mode page query to Android/UFS devices only did not seem appropriate. Bart: How about wrapping access to that mode page in GROUP_SUP and RSCS? It would be nice if we could key off a VPD or two before attempting the MODE SENSE... -- Martin K. Petersen Oracle Linux Engineering
