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Re: user-space device drivers - hurd

From: Marco Gerards
Subject: Re: user-space device drivers - hurd
Date: Wed, 14 Sep 2005 18:03:50 +0200
User-agent: Gnus/5.1007 (Gnus v5.10.7) Emacs/21.3 (gnu/linux)

Shakthi Kannan <shakstux@yahoo.com> writes:


> But, I am looking for some basic (hello world?)
> example to understand how the device interfaces in GNU
> Hurd:
> http://www.gnu.org/software/hurd/gnumach-doc/mach_10.html#SEC89
> interact with its particular GNU mach driver
> probe/open/close/read/write function in gnumach.
> In GNU/Linux kernel, we register a driver with the
> kernel and use device major and minor numbers. I am a
> little lost with gnumach and gnu hurd.

Devices are opened from the Hurd by using device_open.  The name of
the device is passed to this function.  Somehow the kernel figures out
which driver is responsible for the device with a specific name.

For example (from console-client/pc-kbd.c):

 err = device_open (device_master, D_READ, "kbd", &kbd_dev);

After that data can be read from this device:

 error_t err = device_read_inband (kbd_dev, 0, -1, 1,
                                  (void *) &next, &data_cnt);

So that is how devices are accessed from the Hurd.  You could follow
the path from there.  It ends at kbdread in i386/i386at/kd_event.  So
you can also follow the path in reverse.


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