On Thu, Jun 27, 2013 at 03:32:20PM +0200, Reinhard Max wrote: > On Thu, 27 Jun 2013 at 07:17, Greg KH wrote: > > >On Wed, Jun 26, 2013 at 12:03:23PM +0200, Reinhard Max wrote: > > > >>OTOH, why should a driver impose such a limit at all [...] > > > >Because that's the way the driver has successfully worked for the > >past 10+ years? > > Well, this particular part was added less than four years ago[1], > apparently based on experiments that a single person did on a single > device (a PL2303HX as per the comment). I've contacted him to find > out if he still has access to that device and could double-check his > findings. > > Meanwhile I found "Datasheets" dating from 2004 for the PL2303X[2] > to 2012 for newer variants like PL2303HXD[3] and PL2303SA[4] that > have sentences like the following in their "Introduction" chapter: > > "The flexible baud rate generator of PL-2303HXD could be programmed > to generate any rate between 75 bps to 12M bps." > > "The flexible baud rate generator of PL2303SA also could be > programmed to generate any rate between 75 bps to 115 kbps by driver > customization." > > But there are also datasheets for the original PL2303 and PL2303H > from 2002[5] and 2005[6] that do not contain such a statement. None of those datasheets really help as they do not describe exactly how to set the baud rates (or much anything else), so we can't rely on them at all, sorry. > >Again, remember, this driver was created by reverse engineering > >the protocol, the fact that it works at all is amazing. > > I am very well aware of that. > > But still, if the worst thing that might happen when an invalid data > rate is selected is that 9600 baud is used instead, I'd prefer that > over a driver that by trying to be clever keeps me from using data > rates that my hardware would perfectly support. But we don't know if your hardware supports that, that's the problem. > Things would of course be different if setting unsupported baud > rates caused the hardware to crash, but I think there is no > indication of this being the case for any member of the PL2303 > family. We have no idea what happens if you try to do this on old devices, do you? Why not just go buy a device that we know works properly, instead of doing these guessing games? greg k-h -- 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
