This is a respin of previously discussed RFC patch[1]. *Why?* USB gadget can be composed from userspace using ConfigFS. During gadget composition user has to create at least one instance of function. Instance is being created using cd <configfs-root>/usb-gadget/<gadget-name> mkdir functions/<type>.<instance> Where: instance - unique name for instance of function of given type type - name registered by USB function driver during it's module init Instance is a string which allow to identify instance if we have for example two acm functions in one gadget. Type is a USB function driver identifier registered by driver during module init. This string is also a part of USB function module alias. User has to know that functionfs module is identifed using ffs and source sink is identified by SourceSink. When function is compiled as a module user may read module.alias file and get those names form module alias. When function is compiled-in kernel it doesn't provide entry in module.alias file and currently there is no way to learn what functions are available. *Does similar problem exist in other place?* Yes, similar problem is with file systems. Each module which provides file system implementation registers some file system name which can be used during mounting (-t option). User may also check the module.alias file to find fs types available as modules. To discover what fs types has been compiled-in kernel there is a /proc/filesystems file which exports names of all fs types currently registered in framework. *How to solve this?* This patch solves our problem by adding /proc/usb-functions file which exports to userspace list of all currently registered USB function drivers. This is similar solution as one used by file systems. I'm aware that adding new files to proc is not very well welcome. I have looked for some other more suitable location for this list but didn't find any, so suggestions are very welcome. Footnotes: 1 - http://www.spinics.net/lists/linux-usb/msg115872.html Best regards, Krzysztof Opasiak Samsung R&D Institute Poland Samsung Electronics Krzysztof Opasiak (1): usb: gadget: composite: Provide list of registered functions drivers/usb/gadget/configfs.c | 53 ++++++++++++++++++++++++++++++++++++++++ drivers/usb/gadget/configfs.h | 2 ++ drivers/usb/gadget/functions.c | 13 ++++++++++ 3 files changed, 68 insertions(+) -- 1.7.9.5 -- 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
