RFC: Backport HID-logitech to 3.10?

Hi all,
I received a question regarding back-porting the support for the G29
racing wheel to 3.10 (Android in particular), and after some collaborative
work we determined that changes between 3.10 and 4.7 are actually pretty
minimal and self contained.

After copying the HEAD 'hid-lg.[ch]' and 'hid-lg4ff.[ch]' from 4.7, there
is a minimal patch (example attached) required to get the build working.


My question to the list would be how this would/could be implemented, and
how the process works as 3.10 moves through the mainline patches to reach
current HEAD.

Any hints that anyone has would be appreciated.
Simon.

Hi Simon,

On Thu, Sep 1, 2016 at 2:56 AM, Simon Wood [off-list ref] wrote:

Hi all,
I received a question regarding back-porting the support for the G29
racing wheel to 3.10 (Android in particular), and after some collaborative
work we determined that changes between 3.10 and 4.7 are actually pretty
minimal and self contained.

After copying the HEAD 'hid-lg.[ch]' and 'hid-lg4ff.[ch]' from 4.7, there
is a minimal patch (example attached) required to get the build working.

Don't you need hid-logitech-hidpp too?

My question to the list would be how this would/could be implemented, and
how the process works as 3.10 moves through the mainline patches to reach
current HEAD.

Not sure I understand exactly what you want from us here.

The stable rules are detailed in
Documentation/stable_kernel_rules.txt. And unfortunately, I don't
think adding these patches will be acceptable for upstream 3.10.
The rule of thumb is that if a distribution wants to backport changes,
they can have their own rules but the official stable tree is only for
fixing issues, not adding new device support, unless it's *very* small
("- New device IDs and quirks are also accepted.")

So if you need to backport the changes to the 3.10 tree, see the rules
of the distribution you are working on. Some prefer backporting full
commits only (to keep closer to upstream), others will accept some #if
LINUX_VERSION. In those case, I'd personally rather have a small
header that makes the glue between old code and new one to keep the
code closer to upstream.

Cheers,
Benjamin

Any hints that anyone has would be appreciated.
Simon.

On Fri, September 2, 2016 3:32 am, Benjamin Tissoires wrote:

On Thu, Sep 1, 2016 at 2:56 AM, Simon Wood [off-list ref] wrote:

quoted

After copying the HEAD 'hid-lg.[ch]' and 'hid-lg4ff.[ch]' from 4.7,
there is a minimal patch (example attached) required to get the build
working.

Don't you need hid-logitech-hidpp too?

Hi Benjamin,
Nope, the 'hid-logitech-hidpp.ko' driver is separate and (for wheels) only
has support for the G920 wheel. Other Logitech wheels are handled by
'hid-logitech.ko'.

Not sure I understand exactly what you want from us here.

A puppy. ;-)

The stable rules are detailed in
Documentation/stable_kernel_rules.txt. And unfortunately, I don't
think adding these patches will be acceptable for upstream 3.10.

After reading through these I would agree with you, that this is a
nice-to-have not a need-to-have. So, the patch is here if anyone wants to
use it personally or for a distribution.

Thank you for your comments,
Simon.