This problem has been cropping up with many, many USB storage devices. They just don't handle MODE-SENSE page 8 correctly. Some devices are okay with a 128-byte transfer and others aren't. Some are okay with a 64-byte transfer and others aren't. Some are okay transferring the actual size of the page (as given in the header) and others aren't. Some are okay transferring the minimum amount we actually need (12 bytes IIRC) and others aren't.
Although it may not directly address all the problems that Linus observed, a solution has been floating around in the linux-scsi and usb-storage development lists. It looks to me like it's ready to be merged, although no one has done so yet. Basically, it amounts to a per-device flag that can be inherited by default from the host template or set/cleared specifically by the host driver, rather like the flag for using 10-byte READ/WRITE commands. The flag tells sd.c not to ask for page 8 but to assume a write-through cache. The patch is in http://marc.theaimsgroup.com/?l=linux-scsi&m=106366112221507&w=2 At the moment, this MODE-SENSE page 8 is probably the most severe outstanding problem with the usb-storage driver. I'm all in favor of the patch being adopted (hint, hint...). I've been assuming that the "babble" problem arises because the device either tries to send more than 128 bytes of mode-sense data or because it tries to send the data and the subsequent 13-byte status in the same packet. Whether or not this would be detected as an error depends on the maxpacket size, which depends on the speed of the USB bus. (Maybe the device even tries to send an over-sized packet.) Of course, it's always possible that reading page 8 just triggers a bug in the device firmware, and from then on it's all over. On Mon, 22 Sep 2003, Matthew Dharm wrote: > You say this worked with UHCI 'some time ago'? Perhaps that was before all > this mode page 8 stuff got settled? The MODE-SENSE page 8 stuff was added sometime during the 2.5 development cycle. Before it was put in, quite likely the device would have worked fine with UHCI. Alan Stern ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
