[PATCH] Add DEVICE_OPEN_FLAG_DATA_FORMAT

[Bjørn Mork]

Marcel Holtmann <marcel at holtmann.org> writes:

>> I am asking because it seems we have to add some data interception hooks
>> to cdc_wdm to support MBIM, and I am playing with the idea to let the
>> qmi_wwan snoop on "Set Data Format" messages and just support whatever
>> mode you set.  It can most certainly be done, and it won't be much code
>> either.
>
> instead of doing some magic snooping, I would prefer that we add some
> ioctl that allows us to list supported modes and allow them to change.
> So userspace can make the call here. And not the kernel doing some magic
> behind the scenes.

I'll save us both some time and just assume that you are correct this
time as well :-) Snooping the QMI messages is probably not a good idea.

But I do not think an ioctl is wise either.  Please see
http://www.spinics.net/lists/netdev/msg209401.html

I like the way davem leaves no doubt :-)

While testing the features, I used the new ethtool --show-priv-flags/
--set-priv-flags.  Such an implemetation may be accepted upstream, and
would probably fit your needs as well?  It would use one flag per
feature (RawIP, QoS) and allow you to query and set these using the
ethtool API.

But I still believe adding this at all should be based on need, like
some firmware failing in 802.3 mode or someone actually finding a use
for the QoS header (and documents its usage!).  I don't think we are
there yet.


Bjørn