> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of Manu Gautam > Sent: Thursday, September 26, 2013 12:08 AM > > On 9/26/2013 2:10 AM, Felipe Balbi wrote: > > > > On Tue, Sep 24, 2013 at 03:00:20PM +0530, Manu Gautam wrote: > >> Hi Felipe, > >> > >> I wanted to mention one point with respect to this patch: Below > >> changes in the functionfs.h to add ss_count (super speed descriptors > >> count) in desc_header (which is passed from userspace) make the driver > >> incompatible with existing userspace applications compiled against old > >> header file. Let me know if that is acceptable. We are using this > >> driver with Android for adbd (android debug bridge) and these changes > >> are required to support adb over Super Speed controllers e.g. DWC3 > >> along with changed in adbd to pass SS EP and companion descriptors. > > > > Good you mentioned, it saves me the trouble of reviewing this patch :-) > > > > It's not acceptable to break userspace ABI at all. If you want > > SuperSpeed support on function fs, we need to figure out a way to do so > > without breaking userspace. > > > > This might mean adding a separate userspace interface to be used with > > superspeed. While at that, we might want to add a few bytes of reserved, > > unused space in our structures for situations where we need to add more > > data into it, just to make it slightly future proof. > > > > Thanks for your reply. > As you suggested we can have a different interface for super speed > which would be optional to workaround ABI compatibility issue. > Let me know if below interface looks fine to you, I will then implement > accordingly: Just a suggestion: Instead of a new interface for SuperSpeed, why not just add the new fields to the end of the ffs_data struct? And have the functions that copy the struct to/from userspace check the 'len' value passed in, and only handle the SuperSpeed stuff if the length indicates it is new userspace? -- Paul -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
