Re: Polling file descriptors for synchronous transfers
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Hello Peter
Sorry for not replying sooner. I got quite ill this Monday (and am still not recovered) so it just had to wait. Anyway, I hope you have an Android phone handy. Set it to USB debugging mode, connect it and use the attached archive like so: tar -xzf libadb.tar.gz cd libadb make ./main Note that I have *not* run this yet against a home compiled libusb 1.0.9. That's still on my todo list, but I thought I'd at least give you something. The interesting parts are the calls to libadb_poll(). They all time out even though there is data to read. (What is the correct USB terminology again? Frames?) BR / Klas On Mon, May 28, 2012 at 12:43 AM, Peter Stuge <[hidden email]> wrote: > Hi Klas! > > Klas Lindberg wrote: >> >> I am writing a single threaded application that has a poll/select loop. >> >> I don't need asynchronous USB transfers at all, but I do need to poll >> >> the file descriptors associated with the USB device. >> >> > Why? In the code you showed your single thread seems to be waiting in >> > poll() only for libusb file descriptors. I suggest simply using the >> > sync API if you do not need to consider any other file descriptors. >> >> The application uses processes rather than threads but is intended to >> keep track of a large number of Android devices. The process-oriented >> design lets me simplify a lot of things, but I still need pollable >> descriptors to be able to let each process wait on a fair number of >> event sources. The main loop of each process would become messy if I >> have to introduce a different waiting mechanism for the raw USB level >> handling. Other event sources include sockets opened against TCP ports >> open on the devices, applications developed specifically to monitor >> the "machine park" of devices, etc. > > Thanks for the explanation! > > >> The sync API is rather more complicated to use so I'd rather not, if >> possible. Anyway I don't see how that would make the problem go away, >> but perhaps it does. Can anyone confirm that descriptors behave >> differently when only using the sync API? > > If you use the sync API you do not have to pay any attention to > USB-related file descriptors, libusb handles all events for you. > > (Please note that "descriptor" is a significant term within USB with > a meaning distinct from file descriptors, so remember to be clear > about which ones you mean. :) > > >> Reading is typically not a problem. It's just that I don't want to >> call the functions to do so unless I'm sure there really is something >> to read as I'd otherwise end up with a busy-wait style event loop. I'm >> implementing the ADB protocol as a library that provides functions >> like get_fd(), read(), write(), and so on. Most of it is quite >> straight forward stuff. > > I don't know the ADB details, but it looks like the sync API might > work fine. Is it important that your main event loop does other event > handling while the USB transfer is running? Or is it OK to block > until the USB transfer completes or times out? > > If can block then use the sync API. > > If can not block then create a thread which calls > libusb_handle_events_check() in a loop. > > >> > debug log from running your program. (Build libusb-1.0.9 with >> > --enable-debug as parameter to configure.) >> >> I'll see if I can provide a minimal example that demonstrates the problem. > > Thanks! > > > //Peter > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > libusb-devel mailing list > [hidden email] > https://lists.sourceforge.net/lists/listinfo/libusb-devel ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ libusb-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/libusb-devel |
libadb.tar.gz (8K) |
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