Here are some answers to your question. I don't know if you will find them very helpful...
On Wed, 25 Feb 2004, Juergen Stuber wrote: > Hi, > > I'm currently working to correct the locking problems in the > LEGO USB Tower driver. In the course of that I've read through > the current version of usb-skeleton.c in 2.6.3, and I have > a few questions and remarks: > > - Parallel read and write are impossible due to locking on dev->sem. > Is that ok? It's okay for usb-skeleton. Whether or not it's okay for the LEGO Tower driver is up to you. Anyway, it's not dev->sem that prevents parallel read and write. It's the fact that reads use a blocking USB call. Not to mention the question of whether or not the device itself will support simultaneous reading and writing. > If not, is there a standard way to fix it? Change the read routine to use non-blocking USB calls, the way the write routine does. > This one is bothering me most, as it is currently the same in > the LEGO USB Tower driver. > > - Read and write aren't interruptible and don't support nonblocking I/O. > How important is it to support nonblocking I/O? Importance is a matter for the user to decide, not the kernel developer. > - It would be nice to use a bigger buffer size than the packet size > as that is typical. Then go ahead and do so. > - Shouldn't seeking be forbidden by adding an llseek method > that forbids seeking by returning -ESPIPE? It wouldn't hurt. It's not clear whether it would help. > - I suppose __FUNCTION__ should be replaced by __func__. I've never heard of __func__. If it means something different from __FUNCTION__ then no, it shouldn't be replaced. If it means the same thing, then it would be okay (but probably nonstandard) to do the replacement. > - The module use count is decremented after release, not before as > written in the comment at line 151. So submit a patch to fix the comment. Alan Stern ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
