> The device presented two LUNs on the mass-storage interface. LUN 0 was > the emulated CDROM (named "Mass Storage") and LUN 1 was direct-access > (named "SD Storage"). LUN 0 appeared to work normally, although it > reported Not Ready, No Medium Present errors. LUN 1 did the same > thing, but in its response to the REQUEST SENSE command it set the > additional-sense-length byte to 0x12 instead of 0x0a, for no apparent > reason. This caused usb-storage to assume the device supported SANE > SENSE, which presumably it doesn't. Interesting. Under the windows, the device exposes a CD-ROM (which contains windows SW for it). It also has an micro-SD connector as some kind of "bonus" though I've never used it. > Further REQUEST SENSE commands therefore requested 96 bytes of data > instead of the standard 18 bytes. With LUN 0 this worked okay. But > with LUN 1 it didn't; the device reported a failure of the REQUEST > SENSE. This is what caused usb-storage to issue the device reset. Might be interesting to see what happens with a micro-SD actually in the slot. Also, doing a device-reset on a multi-function device because one of the functions isn't too happy may be a tad harsh no ? > After the reset usb-storage continued to ask for 96 bytes of sense > data, and LUN 1 continued to fail the commands. Hence the repeated > resets. Ok. > Thus the two bugs in the Huawei device are: Incorrect > additional-sense-length byte for LUN 1, and incorrect CSW for a 96-byte > REQUEST SENSE on LUN 1. > > I can see two approaches for working around this. The first is to make > the SENSE SENSE test more discriminating. For example, test for > additional-sense-length values larger than 0x12 instead of larger than > 0x0a. Ben Efros, would this be acceptable? > > The second approach is to add a SINGLE_LUN flag to all the Huawei > entries in unusual_devs.h. It's not clear that this is a good idea; if > one of those devices really does have an SD card then people might want > to be able to use it. They do have an SD slot indeed. Any pointer to the piece of code I can tweak to change 0xa to 0x12 (SENSE stuff) to see if that helps ? Cheers, Ben. > Alan Stern > > -- > To unsubscribe from this list: send the line "unsubscribe linux-usb" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
