On Tue, Jun 06, 2006 at 10:10:58AM -0300, Luiz Fernando N. Capitulino wrote: > On Tue, 6 Jun 2006 00:34:41 -0700 > Greg KH <[EMAIL PROTECTED]> wrote: > > | On Sat, Jun 03, 2006 at 07:19:17PM -0300, Luiz Fernando N. Capitulino wrote: > | > On Fri, 2 Jun 2006 15:44:35 -0700 > | > Greg KH <[EMAIL PROTECTED]> wrote: > | > > | > | On Fri, Jun 02, 2006 at 03:41:21PM -0700, Pete Zaitcev wrote: > | > | > On Fri, 2 Jun 2006 13:50:14 -0700, Greg KH <[EMAIL PROTECTED]> wrote: > | > | > > On Fri, Jun 02, 2006 at 12:03:14AM -0300, Luiz Fernando > N.Capitulino wrote: > | > | > > | > | > > > 2. The new pl2303's set_termios() can (still) sleep. Serial > Core's > | > | > > > documentation says that that method must not sleep, but I > couldn't find > | > | > > > where in the Serial Core code it's called in atomic context. > So, is this > | > | > > > still true? Isn't the Serial Core's documentation out of > date? > | > | > > > | > | > > If this is true then we should just stop the port right now, as the > USB > | > | > > devices can not handle this. They need to be able to sleep to > | > | > > accomplish this functionality. > | > | > > > | > | > > Russell, is this a requirement of the serial layer? Why? > | > | > > | > | > Shouldn't it be all right to schedule the change at the moment of > | > | > that call and have it happen later? Resisting a temptation to abuse > | > | > keventd and schedule_work and using a tasklet may help with latency > | > | > enough to make this tolerable. > | > | > | > | Some devices require more than one usb message to set all of the proper > | > | termios bits in the device. Creating a way to queue them up and fire > | > | them off later, and handle errors if something happened in the middle, > | > | after we told userspace the termios change succeeded, might get quite > | > | messy :( > | > > | > But set_termios() returns nothing, and look what termios > | > man page says about tcsetattr() return value: > | > > | > """ > | > Note that tcsetattr() returns success if any of the requested changes > could > | > be successfully carried out. Therefore, when making multiple changes it > may be > | > necessary to follow this call with a further call to tcgetattr() to check > that > | > all changes have been performed successfully. > | > """ > | > | Good point, I forgot about that. > | > | > Also, why do they need to sleep? Did you note that my version of > | > set_mctrl() is atomic? > | > | Yes, that looks "atomic" in a way, but when the function returns, the > | value is not really set. It only happens some time in the future when > | the urb completes (and hopefully it works, no retry is allowed...) > | > | So it might be a bit "racy" :) > > Oh, that's true. > > Is it acceptable?
I don't think so. > The hardware is capable to queue URBs, right? Yes it is. thanks, greg k-h _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
