Hi, On Fri, Nov 30, 2012 at 04:07:22PM +0100, Michal Nazarewicz wrote: > On Fri, Nov 30 2012, Felipe Balbi wrote: > > Hi, > > > > On Thu, Nov 29, 2012 at 05:43:21PM +0100, Sebastian Andrzej Siewior wrote: > >> |# modprobe dummy_hcd num=2 > >> > >> |# find /sys/kernel/config/ -ls > >> > >> | 557 0 drwxr-xr-x 3 root root 0 Nov 29 17:26 /sys/kernel/config/ > >> | 558 0 drwxr-xr-x 5 root root 0 Nov 29 17:26 /sys/kernel/config/usb_gadget > >> | 561 0 drwxr-xr-x 4 root root 0 Nov 29 17:26 /sys/kernel/config/usb_gadget/udcs > >> | 569 0 drwxr-xr-x 2 root root 0 Nov 29 17:26 /sys/kernel/config/usb_gadget/udcs/dummy_udc.1 > >> | 568 0 drwxr-xr-x 2 root root 0 Nov 29 17:26 /sys/kernel/config/usb_gadget/udcs/dummy_udc.0 > >> | 560 0 drwxr-xr-x 2 root root 0 Nov 29 17:26 /sys/kernel/config/usb_gadget/gadgets > >> | 559 0 drwxr-xr-x 2 root root 0 Nov 29 17:26 /sys/kernel/config/usb_gadget/functions > >> > >> | # lsmod > >> | Module Size Used by > >> | dummy_hcd 20287 0 > >> | udc 10219 1 dummy_hcd > >> > >> |# mkdir /sys/kernel/config/usb_gadget/functions/acm.one > > > > I dont think this is enough. It doesn't cope with multiple > > usb configurations. > > > > Or is this just to show how we could probe functions to the framework > > before even binding them to a UDC ??? > > This loads function without even creating a gadget. This would allow > the same function to be used in several different gadgets. why would you load a function before it's actually needed ? We could end up with users who will just load the function and never actually need them which will consume memory for no reason. > > Anyway, what I wanted to see was something like: > > > > # mkdir -p /sys/kernel/config/usb_gadget/dwc3.0/gadget0/config0 \ > > /sys/kernel/config/usb_gadget/dwc3.0/gadget0/config1 > > > > # echo acm.2,obex.3,msc > \ > > /sys/kernel/config/usb_gadget/dwc3.0/gadget0/config0/functions > > > > # echo ffs,sourcesink > \ > > /sys/kernel/config/usb_gadget/dwc3.0/gadget0/config1/functions > > I think that the idea expressed here was so far to use (symbolic) links > to bind functions to configurations. I understood that much, thank you ;-) > > Then when you echo the function name to the functions file under the > > configuration, if the function isn't registered, then a try_module_get() > > will tell udev to load it and increment the usage counter. Also, it will > > create files and other directories for every part of the every > > descriptor, but, of course, only strings will be writable, everything > > else is read-only. > > > > This means that the following should allocate and expose a device > > descriptor: > > > > # mkdir /sys/kernel/config/usb_gadget/dwc3.0/gadget.0/ > > # ls /sys/kernel/config/usb_gadget/dwc3.0/gadget.0/ > > Again, so far it seems everyone on the list thought to rather link > a gadget to UDC via symlinking and keep UDCs and gadgets in separate > directories. > > > Does that make sense to you ??? It would remove the need to even > > create a functions/$function.$num directory for everybody before being > > able to use the function. The way you've setup configfs it means that > > if I'm going to use ACM on multiple configurations or even multiple > > gadgets, I will have to know how many of them I will need before hand. > > Not necessarily. If you are not interested in sharing functions between > gadgets, all you have to do is use unique prefix for the functions, for how do you know how many tty ports u_serial needs to create beforehand ? You just don't know... Granted, my approach will have the same limitation. But anyway, the point is that sharing functions can be a bit dangerous I guess. We need to have separate instances for each user IMHO. What if you have a system with 2 UDCs then you link the same acm.blah-0 to both UDCs and try to transfer on both of them at the same time ? If you have separate instances that wouldn't be an issue at all. -- balbi
Attachment:
signature.asc
Description: Digital signature
