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Re: [ddccontrol-devel] [RFC] A common platform usb/ddc/anythingelse ?
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From: Oleg I. V. <ol...@cs...> - 2006-03-06 10:17:00
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Hi,
Fr=C3=A9d=C3=A9ric, we should avoid writing kernel modules. The reaso=
n is that=20
this would complicate ddccontrol installation.
Have you considered using libusb to access USB devices? This library =
is=20
specially designed to access usb devices from the userspace. Check this=20
link: http://libusb.sourceforge.net/ This library is currently ported to=20
several platforms, including MacOS X.
Nicolas: as for ddccontrol integration. Perhaps, it's good idea to=20
create something like a ddcusb application which should provide interface=
s=20
similar to ddcpci and add usb: namespace to the ddccontrol.
Regards,
Oleg.
----- Original Message -----=20
From: "Fr=C3=A9d=C3=A9ric 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/anythinge=
lse=20
?
> Le vendredi 03 mars 2006 =C3=A0 21:26 +0100, Nicolas Boichat a =C3=A9cr=
it :
>> Hi Fr=C3=A9d=C3=A9ric,
>>
>> On Tue, 2006-02-28 at 22:12 +0100, Fr=C3=A9d=C3=A9ric 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,=20
>> > 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 hardwar=
e
> 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 i=
t
>> 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=20
> 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 d=
o
> 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 sourc=
e
> 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 b=
e
> 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/.../brigthnes=
s
> 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-standar=
d
>> 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=20
> 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 wil=
l=20
> use and contribute to libhid.
> The big advantage is to have it working on Linux, Mac osX, Bsd (put you=
r
> favorite os here) ...
>
>> I would be happy to help you add support for USB devices. When you hav=
e
>> 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 repor=
t=20
> descriptor.
> lsusb -vvv don't work because the monitor is grabbed by linux hid layer=
,=20
> 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.
>
> Fr=C3=A9d=C3=A9ric
>
>
>
>
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