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 Isn't the Serial Core's documentation out of date?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? The hardware is capable to queue URBs, right? -- Luiz Fernando N. Capitulino _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
