Hi Ilya,
ilya wrote:
hello,
my name is ilya, i am a kernel newbie, and i just
joined the list in hopes of getting some insight on
linux device driver development.
i am writing a kernel-mode driver for a pci card and
i need a mechanism to control the device via user-space
application. at first i had an additional character driver
initialized along with my driver and using fread/fwrite
i would transfer info back and forth. then i found out
about sysfs, so now i am using files in sysfs to
send "commands" to the driver and receive data back.
i have a feeling, however, that i am abusing this method.
what is the appropriate way of setting this up?
IIRC, sysfs documentation in the kernel sources does not seem to state
what is permitted and what not when it comes to the sysfs usage. All it
does is line up few rules and limitations - I guess if you could live
with that, then that is the way to do it, too ;)
is there
a way for the module to notify an application of some
event happening?
By using select/poll from the userspace one needs to implement similar
procedure in their (character) device driver as well - namely poll().
This would (if properly implemented) relieve you of the need to manually
check for an event to happen. See LDD3 (http://lwn.net/Kernel/LDD3/) for
sample device driver that utilizes the poll() syscall.
because right now i do this by
constantly reading from one of the files in sysfs until
the value it holds changes. i also know that reading
files from kernel-mode is not a good thing, but i want
to implement something of a config file that can be
modified from user-space but would be read in by
the module. what is the best way of doing this?
I would go with one of these options:
a) use write() or ioctl() syscall to pass the parameters from the
userspace to the kernel driver,
b) use sysfs to supply the parameters to the kernel
Both ways deal with predefined structure being constructed, filled with
the parameter values and fed to the driver by the means of either using
syscalls or sysfs interface.
Maybe someone else has some other way of doing it...
Regards,
Hinko
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