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Re: [ddccontrol-devel] [RFC] A common platform usb/ddc/anythingelse ?
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From: Nicolas B. <ni...@bo...> - 2006-03-06 12:31:20
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Hi Oleg, Thanks for your message, Frédéric and I are in active discussion, off-list (and in French as it's easier for both of us .-)). As far as we know, there is three methods to access USB HID devices: - hiddev, really simple, just like i2c devices, but unfortunately it doesn't seem to work. - libhid over libusb, but it would require a kind of application like ddcpci, as it requires to be root (but it would work on many platforms, not only Linux). - a new kernel module, which of course is not the best solution. We are trying these methods one by one, starting with hiddev, and I hope we won't need to create a kernel module... Best regards, Nicolas On Mon, 2006-03-06 at 13:16 +0300, Oleg I. Vdovikin wrote: > Hi, > > Frédéric, we should avoid writing kernel modules. The reason is that > this would complicate ddccontrol installation. > > Have you considered using libusb to access USB devices? This library is > specially designed to access usb devices from the userspace. Check this > link: http://libusb.sourceforge.net/ This library is currently ported to > several platforms, including MacOS X. > > Nicolas: as for ddccontrol integration. Perhaps, it's good idea to > create something like a ddcusb application which should provide interfaces > similar to ddcpci and add usb: namespace to the ddccontrol. > > Regards, > Oleg. > > ----- Original Message ----- > From: "Frédéric Leroy" <fr...@st...> > To: "Nicolas Boichat" <ni...@bo...> > Cc: <ddc...@li...> > Sent: Saturday, March 04, 2006 1:46 AM > Subject: Re: [ddccontrol-devel] [RFC] A common platform usb/ddc/anythingelse > ? > > > > Le vendredi 03 mars 2006 à 21:26 +0100, Nicolas Boichat a écrit : > >> Hi Frédéric, > >> > >> On Tue, 2006-02-28 at 22:12 +0100, Frédéric Leroy wrote: > >> > Hello, > >> > > >> > I own an Apple Studio display without button to control it (which > >> > integrates an usb hub) . > >> > Long ago, I tried ddcci, without success. It was at alpha stage, > >> > without > >> > graphical user interface, but the monitor didn't seem to support ddc > >> > interface. > >> > >> It would be nice if you could check quickly that it still doesn't > >> work .-) Just in case... So we are sure we don't do useless work .-) > > I read nowhere it is capable of that. But, meanwhile, I had new hardware > > so I'll try again and keep you in touch. > > > >> Nice, btw, do you know this document: > >> http://www.usb.org/developers/devclass_docs/usbmon10.pdf . It could be > >> useful. > > I have this document thanks to your project :). I made some research on > > usbmon, vcp, mccs ... but I didn't found anything interesting. > > On vesa.org the standard can be buy for 350$+70$shipping IIRC ... > > *ouch* ! > > Once the project is good enough to have audience, maybe we could set up > > a paypal page to buy it and level up the vesa controls. > > > >> As far as I know, controlling monitors using USB or DDC/CI is very > >> similar (the only problem I see is caps string, but it's not a major > >> issue). It also uses controls, and the protocols are very near, so we > >> could keep the database, and most of the current program. So I think it > >> is feasible to integrate USB support directly into ddccontrol, without > >> having 2 sets of tools. > > In usbmon, IIRC, it is written that vesa control page are made to > > standardize controls, for any bus access. > > There always be some minor difference in implementation, but basically, > > as I understand usbmon, vcp are the same for ddc/ci, usb, whatever. > > Then, It was obvious for me to contact you :) > > > >> I already played a little with HID usb devices, but I don't remember > >> very well the details. I don't know where you got so far, but here are > >> some questions: > >> Could you explain how do you interact with the monitor? Do you need a > >> specific driver, or HID usb module is enough? Do you need a library > >> (libusb? libhid?), or could you directly open a device (/dev/hiddev* > >> devices?)? Is it possible for a non-root user to write to the device (by > >> setting the permissions to device?)? > > Long ago, I tried first to use /dev/hiddev, without success. > > Today, I just have some quick hacks in libhid and the test program to do > > only one settings. So, basically, I have no code, but I know it is > > working. > > > > Since yesterday, I'am reading linux kernel litterature and kernel source > > to make a kernel driver. After all, it's an hid device, and thus, must > > have it own kernel driver. > > > > I plan to do a kernel driver totally integrated with usb, hid device. > > To use the control, I would use only sysfs, as I don't see how it can be > > an input driver. > > > > So, something like : > > /sys/.../display/displayname/brightness_min # minimal value > > /sys/.../display/displayname/brightness_max # maximal value > > /sys/.../display/displayname/brightness # setting > > and maybe > > /sys/.../display/displayname/unsupported_vcp/0xfe # meaning missing ... > > /sys/.../display/displayname/vcp/0x10 # link to /sys/.../brigthness > > to /sys/.../brigthness > > > > Permission for controls are my big problem. I'm weak on this. > > basically, the files above would have these permission, accorded to the > > settings : > > /sys/.../degauss root:vcp --w--w--- > > /sys/.../brightness root:vcp -rw-rw--- > > /sys/.../horizontal_frequency root:vcp -r--r---- > > > >> Needing a non-standard kernel module should be avoided, as it > >> complicates installation (and packagers' work too). Using a standard > >> kernel module like usbhid is ok. > > I totally agree > > > >> Needing a standard library like libusb is ok, libhid looks non-standard > >> as far as I can tell (it is not even included in Gentoo), so avoid it if > >> you can. > > libhid is very young and not very easy to deal with (I have to be root to > > grab the usb device). > > But, it's for me a nonsense to use libusb, as I will have > > to borrow the parser of libhid ... so if I make a user interface, I will > > use and contribute to libhid. > > The big advantage is to have it working on Linux, Mac osX, Bsd (put your > > favorite os here) ... > > > >> I would be happy to help you add support for USB devices. When you have > >> working code, it would be nice if you could send to the list some > >> example programs (get monitor ID (or the complete EDID), read or write > >> from a control, enumerate supported controls (all these are essential > >> features), and everything else you found out that you think is > >> interesting), and some example output. > > I'll need your help also. I have only one monitor to test. > > I would be happy if user who own an usb monitor, sends me the hid report > > descriptor. > > lsusb -vvv don't work because the monitor is grabbed by linux hid layer, > > it needs to unload > > usbhid driver first I guess :( If someone has an easy solution to get > > the report, tell me ! > > Or I can make a quick and dirty prog to do this. > > > >> Then we will discuss how to integrate it in ddccontrol, and I'll give > >> you a CVS access so you can work more freely. > > I post to this list because I believe these two project are linked. I > > prefer to discuss first and code after :) At least, warn you that I'll > > maybe come back with something to integrate. > > I code quite slowly, so it will take some time before I come back with > > an alpha version of the kernel driver. In any case, I'will post my work > > on this list. And once it's mature enough, on kernel usb mailing list > > (unless I use only libhid). > > > >> Thanks for your interest in this project, > > It's natural ... > > > >> Meilleures salutations, > > Les formules de politesses ne sont pas mon fort, mais le coeur y est ! > > I hope your project to be successful. > > > > Frédéric > > > > > > > > > > ------------------------------------------------------- > > This SF.Net email is sponsored by xPML, a groundbreaking scripting > > language > > that extends applications into web and mobile media. Attend the live > > webcast > > and join the prime developer group breaking into this new coding > > territory! > > http://sel.as-us.falkag.net/sel?cmd_______________________________________________ > > ddccontrol-devel mailing list > > ddc...@li... > > https://lists.sourceforge.net/lists/listinfo/ddccontrol-devel > > |
