On Tue, 10 Jan 2017, Dainius Masiliūnas wrote: > (I pressed reply instead of reply to all, sorry. Resending this.) > > On Tue, Jan 10, 2017 at 8:29 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > There _is_ a quirk for broken models. However, we don't know how > > complete the set of quirk entries is, so we err on the side of caution. > > Then what is it used for? There doesn't seem to be much point in a > blacklist when the functionality is disabled by default to begin with. It is used for preventing the kernel from issuing a READ CAPACITY(16) command to the device. Normally the kernel would do this if the reply to READ CAPACITY(10) indicated there were more than 2^32 blocks (about 2 TB). > And if there's a whitelist, does it mean that we should submit the IDs > of working USB devices for whitelisting? Also, is there a module > parameter to toggle the functionality, to facilitate testing whether > the device works fine or not? There is no whitelist, but there is a quirk flag for devices that require READ CAPACITY(16) instead of READ CAPACITY(10) (because READ CAPACITY(10) returns incorrect information). In theory, I suppose we could change the kernel so that it would default to READ CAPACITY(16) for devices that report a SCSI level >= 3, or something along those lines. In general we hesitate to make changes of this sort, because they almost always end up breaking _some_ devices -- and if that happens then the change is reverted, with no exceptions. Linus has a very strict rule about not breaking working systems. Alan Stern -- 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
