Uli,
Ulrich Kunitz wrote:
Larry,
I've not read your patches your detail, so I comment only on your
description.
The problem is the driver doesn't have good ideas, whether the
device is outdoor and in which country it operates. Devices have
some information available, but I have definitely a device
marketed in Canada, which had an EEPROM value for ETSI as
regulatory domain. I would expect the daemon to know, in which
country it is and whether the device is used outdoors. Keep also
in mind, that this information will be available from the AP at a
later time.
I agree that once the AP is broadcasting the country code, this all gets easier. I have a problem
similar to yours in that my interface's EEPROM supplies a code that indicates the world, which leads
to the bcm43xx driver code setting 2.4 GHz channels 1 - 14 and then running active scans on all of
them. Of course in the US 12, 13 and 14 are illegal and could lead to legal action if the FCC were
monitoring outside my house.
I don't see any means for the daemon to know its country other than the driver or the user telling
it. If such a means exists, I would like to learn of it. My current working model is to supply the
country code from a module option when the driver is loaded.
So there should be an explicit method to request the minimum set
or the configuration of daemon. Later the set can be changed again
by the AP information provided.
If the daemon is not running, if the country code is " ", or if it doesn't match any country in the
database, the minimum set is supplied, but the driver could call the routine again if it learned
more about its environment.
b) It then creates a new directory, '/proc/net/ieee80211_geo', and
populates it with 2 files for communication with the daemon. The first,
which is read by the daemon, contains the country and outdoor codes, and
the second is for the the daemon to write the 'struct ieee80211_geo' data
corresponding to the country and indoor/outdoor information passed from the
kernel.
Michael Buesch already commented on /proc/net. I don't think, that
this will be popular with a lot of folks. sysfs should be
supported and the mechanism should be comparable to firmware
loading. Maybe this could be some kind of udev extension. And make
it device specific, the whole approach should not break, if you
are accessing two devices connecting to two different access
points at the same time, where one of them is configured by the
central networking folks, who don't bother to adapt there configs
to specific countries and the other is a perfectly conformant
local AP, which is used for "testing" purposes.
Based on Michael's comments, I have changed the kernel - user space communication to use sysfs
rather than procfs. It also uses only a single mode 0666 file in /sys for communication. The deamon
spins waiting for that file to exist, then reads it to get the country and in/out flags. It then
writes the geo binary data to the file, closes it, delays a while and then repeats. After the geo
data are read, the kernel routine deletes the kobjects that create the sysfs file, loads the geo
data into the location supplied by the driver, and exits. Because the /sys file exists for only a
short time, I don't think that having it world writable will cause any problems. In addition, the
data supplied are thoroughly checked to make sure that it has the proper data for geo information.
If the 0666 mode is a problem, the daemon may have to become root to write the data.
Because, the geo data is loaded into a data area that is specific to each device, I don't expect any
problem with the situation you describe even if the same driver is operating both devices. If I have
missed some nuance, please enlighten me.
2. The user-space daemon, which need not be run as root, does the following:
It needs only to run temporarily run as root. I would definitely
recommend that all file parsing activities should not run as root.
At present, it does everything as an unprivileged user.
e) It then spins waiting for the existence of file
'/proc/net/ieee80211_geo/country', which is the indication that the kernel
is requesting data.
Again the whole interface should be device specific.
This part I don't understand. Everything in the geo data is generic to ieee802.11 devices. As I
stated earlier, it will end up in the private data for the device, but I don't see any reason for
the daemon to know which device is going to use the data.
Thanks for your comments,
Larry
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