On Tue, 12 Sep 2006, Vivek Dharmadhikari wrote: > Alan > > > The bytes of the two CBW packets are otherwise identical? > > Yes the CBW packets are identicle except the value of Tag field. The > difference in the value of Tag field do not bother me because it can > vary.
Yes. > > > Is it possible that the large gap of 12ms confuses the device ? > > > > It should not be possible. > > I too thought the same way. I think,the presence of SOF should be good > enough for the device to stay tunned regardless of the timegap between > previous and next command. That's right. > > The only reason I can think of for the difference in behavior > > would be if the device didn't receive the data1 packet > > correctly. But that seems very unlikely. > > I see that the device is receiving data1 packet. No you don't. All you know is that the USB bus analyzer receives the data1 packet. Perhaps the device doesn't receive it properly. For example, maybe the signal strength is right at the borderline, so that the analyzer can understand the signal but it's just a little too weak for the device to receive it properly. Or maybe the timing jitter in the bits is right at the borderline. This would explain why the device doesn't send back an ACK packet. > > Have you tried this with a different device? Maybe a > > different brand of USB flash memory device will work better. > > Yes we have tried several brands of USB flash memory(ohci/ehci) and they > work well with our system. We haven't seen any devices failing in a > similar fashion. But only this particular USB stick do not work with our > system. We want to make this rogue USB device works with our system as > well. On the other hand, this rogue device works well with Linux and > Windows PC -:( This indicates you have a minor hardware incompatibility between the embedded host and that particular device. I've seen this sort of thing before. For example, I have a USB disk drive enclosure and cable that operates okay with my computer at work. But with my computer at home it fails. If I switch cables then it works. Or I can use the same cable with a different mass-storage device at home, and then the cable works. So which component is faulty -- the computer, the cable, or the enclosure? > How do the HOST driver cope with such rogue devices ? Early on, you > mentioned about blacklist table. We know that the device always fails to > ack to mode sense(6) packet. Is it possible to use blacklist table to > avoid sending mode sense(6) command ? Yes it is possible, but there's no reason for it if only one computer fails with only one device. For all you know, a different POCKET USB disk might work okay with no need for a blacklist entry. But if you want to create one anyway, this is how to it. Edit unusual_devs.h in drivers/usb/storage/ in the kernel source. Add an entry for the POCKET USB device, with the appropriate vendor, product and revision numbers, and use the US_FL_NO_WP_DETECT flag. Alan Stern ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
