|From:||Michal Nazarewicz <email@example.com>|
|Subject:||[PATCHv3 0/7] The FunctionFS composite function|
|Date:||Fri, 16 Apr 2010 11:49:25 +0200|
|Cc:||Michal Nazarewicz <firstname.lastname@example.org>, Greg KH <email@example.com>, Kyungmin Park <firstname.lastname@example.org>, Marek Szyprowski <email@example.com>, Davide Libenzi <firstname.lastname@example.org>, Thomas Gleixner <email@example.com>, firstname.lastname@example.org, email@example.com|
Hello everyone, *Changes from Previous Version* This is the second version of the FunctionFS patchset. 1. Changed wait_event_interruptible_locked() implementation and removed _irqsave variants (per Thomas Gleixner's comment). See the first patch. 2. Fixed the fs/timerfd.c patch (again, the bug has been spotted by Thomas). See the second patch. 3. Comments pointing to <URL:http://www.linux-usb.org/usbtest/> added to testusb.c and the introductory commit (added after comments from David Brownell). See the commit message of the last but one patch and beginning of the last patch. *Prologue* Patches that follow implement the FunctionFS composite function that is a conversion of GadgetFS to use the composite framework. Possible uses are: 1. what Peter Korsgaard has described: > I could certainly imagine doing something like that, E.G. reuse the > existing g_serial functionality while implementing E.G. a HID device > though gadgetfs. 2. or what Rupesh Gujare has described: > In my requirement, I want to have Media Transfer Protocol (MTP) > (which uses user level usb driver (usb.c) & gadgetfs) along with > modem functionality(f_acm.c). > > Currently either of them ie. f_acm (as part of composite driver > along with ums) or gadgetfs (as independent module) can be loaded, > which allows only one active USB function at a time. > > If gadgetfs can be made as a composite function then I can have both > functionality at same time. *The Patches* The first patch creates a new wait_event_interruptible_locked() interface for waiting on events. While holding the wait queue's lock. Refer to the commit message for usage. The second patch makes use of the new interface in fs/timerfd.c file replacing some 20 lines by a single macro call. Next three patches implement the FunctionFS and a composite gadget that uses FunctionFS and Ethernet function (with the later function optionally disabled via Kconfig). The last three patches provide a testing code for the FunctionFS. My original intend was to provide those just for anyone who'd like to test the code and not to include them in the Linux source tree but if that seems appropriate then why not? *How FunctionFS works* (Copied from third patch commit message.) From kernel point of view it is just a composite function with some unique behaviour. It may be added to an USB configuration only after the user space driver has registered by writing descriptors and strings (the user space program has to provide the same information that kernel level composite functions provide when they are added to the configuration). This in particular means that the composite initialisation functions may not be in init section (ie. may not use the __init tag) hence the first and fourth patch in the series. From user space point of view it is a file system which when mounted provide an "ep0" file. User space driver need to write descriptors and strings to that file. It does not need to worry about endpoints, interfaces or strings numbers but simply provide descriptors such as if the function was the only one (endpoints and strings numbers starting from one and interface numbers starting from core). The FunctionFS changes numbers of those as needed also handling situation when numbers differ in different configurations. When descriptors and strings are written "ep#" files appear (one for each declared endpoint) which handle communication on a single endpoint. Again, FunctionFS takes care of the real numbers and changing of the configuration (which means that "ep1" file may be really mapped to (say) endpoint 3 (and when configuration changes to (say) endpoint 2)). "ep0" is used for receiving events and handling setup requests. When all files are closed the function disables itself. *Testing* The fifth patch implement a simple source/sink FunctionFS driver based on similar driver for GadgetFS by David Brownell. It registers a dual-speed function with a single IN and single OUT endpoints. The sixth and seventh patch provide a host-side testing code. This is what David Brownell has created a while back with a simple fix to make the tool detect the number of our source/sink interface. Still, you will need to configure the gadget to report idProduct == 0xa4a4 (an "echo 0xa4a4 >/sys/module/g_ffs/parameters/usb_product" should suffice) or configure host to handle 0x0525:0xa4ac devices using the usbtest driver. Hence, the simplest way to run the test is to do the following: * On target (machine that runs has the gadget) as root: $ echo 0xa4a4 >/sys/module/g_ffs/parameters/usb_product && $ mkdir /dev/ffs && $ mount -t functionfs ffs /dev/ffs && $ cd /dev/ffs && $ /path/to/ffs-test * On host (as root): $ testusb -a At this point I have to admit that communication on EP0 has not yet been tested, so beware of bugs there. *Request for Comments and Future Work* Regarding presented version there are two aspects I'd like to discuss. 1. First of all, the current code uses similar approach GadgetFS used -- there is a single file ("ep0" in case of FunctionFS and named after the controller in case of GadgetFS) that is used to receive events from kernel and handle ep0 communication. I think it is not the best approach as it'd be simpler and cleaner if there were two files: one for receiving events and another for handling ep0 communication. What do you think? Should I keep the current version or change to code to use two files? 2. What still needs to be implemented is a mechanism allowing double buffering (and in effect transmission without pauses) and maybe single-thread user-space driver implementation. I'd like to ask what would be the best way to achieve this. GadgetFS implements asynchronous I/O -- is it still the best option? 3. The last thing I'd like to mention is that the FunctionFS is designed in such a way that with some more work it will be able to mount it several times so in the end a gadget could use several FunctionFS functions. The idea is that each FunctionFS instance is identified by the device name used when mounting. One can imagine a gadget that has an Ethernet, MTP and HID interfaces where the last two are implemented via FunctionFS. On user space level it would look like this: $ modprobe g_foo $ mkdir /dev/ffs-mtp && mount -t functionfs mtp /dev/ffs-mtp $ ( cd /dev/ffs-mtp && mtp-daemon ) & $ mkdir /dev/ffs-hid && mount -t functionfs hid /dev/ffs-hid $ ( cd /dev/ffs-hid && hid-daemon ) & On kernel level the gadget would check ffs_data->dev_name to identify whether it's FunctionFS designed for MTP ("mtp") or HID ("hid"). ____________________________________________________________  http://article.gmane.org/gmane.linux.usb.general/23890  http://article.gmane.org/gmane.linux.usb.general/23902  http://www.linux-usb.org/gadget/usb.c  http://www.linux-usb.org/usbtest/testusb.c David Brownell (1): USB: testusb: an USB testing application Michal Nazarewicz (7): wait_event_interruptible_locked() interface fs/timerfd.c: make use of wait_event_interruptible_locked_irq() USB: gadget: __init and __exit tags removed USB: f_fs: the FunctionFS driver USB: g_ffs: the FunctionFS gadget driver USB: ffs-test: FunctionFS testing program USB: testusb: testusb compatibility with FunctionFS gadget drivers/usb/gadget/Kconfig | 21 +- drivers/usb/gadget/Makefile | 2 + drivers/usb/gadget/composite.c | 21 +- drivers/usb/gadget/config.c | 4 +- drivers/usb/gadget/epautoconf.c | 12 +- drivers/usb/gadget/f_acm.c | 32 +- drivers/usb/gadget/f_ecm.c | 33 +- drivers/usb/gadget/f_fs.c | 2453 +++++++++++++++++++++++++++++++++++ drivers/usb/gadget/f_mass_storage.c | 2 +- drivers/usb/gadget/f_rndis.c | 34 +- drivers/usb/gadget/g_ffs.c | 322 +++++ drivers/usb/gadget/u_ether.c | 4 +- fs/timerfd.c | 25 +- include/linux/usb/functionfs.h | 199 +++ include/linux/wait.h | 149 +++ kernel/sched.c | 1 + tools/usb/ffs-test.c | 554 ++++++++ tools/usb/testusb.c | 547 ++++++++ 18 files changed, 4323 insertions(+), 92 deletions(-) create mode 100644 drivers/usb/gadget/f_fs.c create mode 100644 drivers/usb/gadget/g_ffs.c create mode 100644 include/linux/usb/functionfs.h create mode 100644 tools/usb/ffs-test.c create mode 100644 tools/usb/testusb.c -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to firstname.lastname@example.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Copyright © 2010, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds