Dear Ian, Thanks for taking the trouble to reply. On Wed, Mar 08, 2017 at 11:13:49AM +0000, Ian Abbott wrote: > On 08/03/17 10:08, Cheah Kok Cheong wrote: > >Dear Dan, > > Thanks for reviewing this patch. > > > >On Wed, Mar 08, 2017 at 08:54:47AM +0300, Dan Carpenter wrote: > >>On Sun, Mar 05, 2017 at 03:22:33AM +0800, Cheah Kok Cheong wrote: > >>>If comedi module is loaded with the following max allowed parameter > >>>[comedi_num_legacy_minors=48], subsequent loading of an auto-configured > >>>device will fail. > >> > >>Don't set comedi_num_legacy_minors=48, then? > >> > >>This doesn't seem like the right fix at all. Why only allow one auto > >>configured board? Why not 5 or 10? > >> > > > >Let me explain, the original intended behaviour is to allow user to > >reserve up to 48 minor numbers for legacy devices. > > > >Therefore [sudo modprobe comedi comedi_num_legacy_minors=3] > >will allocate minor number 0, 1, 2 for legacy devices. > >Subsequent loading of an auto-configured device will use minor number 3. > >And the next one number 4 so on and so forth. > > > >Now for the corner case of [comedi_num_legacy_minors=48] which > >is supposed to reserve minor number 0 till 47 for legacy devices, > >and is supposed to allocate number 48 and so on for auto-configured > >devices, does not allocate number 48 anymore after commit > >38b9722a4414. > > Both legacy and auto-configured devices will have minor numbers less than > 48, which is the total number of devices currently supported by Comedi. > Minor numbers 48 and above have been reserved for dynamic allocation to > those Comedi subdevices that support asynchronous commands. > Thanks for the explanation. > >This is due to the changes in comedi_alloc_board_minor(). > > > >As to why I chose to limit [comedi_num_legacy_minors=47], is given > >in the commit log. > > > >This will allow user to allocate 0 till 46 for legacy devices and > >subsequent auto-configured devices will start from 47 and so forth. > > > >I don't think anybody will miss one less number for legacy devices > >otherwise there'll be complains earlier on. > > As Dan implies above, if you want auto-configured devices to work, set > comedi_num_legacy_minors to a value less than 48. Further limiting > comedi_num_legacy_minors to 47 seems a bit arbitrary. > > The comedi_test module mentioned in your commit can still be used when > comedi_num_legacy_minors=48 by configuring a "legacy" comedi_test device. > Most of the other Comedi drivers support "legacy" devices exclusive-or > auto-configured devices. > Ah ok now I understand what Dan is trying to say actually. Thanks for the detailed clarification. Sorry for the inconvenience caused. Thanks. Brgds, CheahKC > >Thanks. > > > >Brgds, > >CheahKC > > > >>regards, > >>dan carpenter > >> > > > -- > -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=- > -=( Web: http://www.mev.co.uk/ )=- _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
