The last couple of days I've once again updated my kernel to current linux-2.6.git and I had to do the manual merge of the apparently abandoned original out-of-tree pcc_acpi.ko driver in order to get brightness control of the LCM on my Panasonic CF-R5 laptop.
I've tried to contact the original author multiple times during the recent years asking about his mainline inclusion plans, with no response so far. So this time finally I decided to submit the driver even without explicit wish by the original author. It was already GPL licensed, so no problems here.
However, the driver didn't yet support the backlight class device API, neither did it support user-configurable keymaps on the input device for the hotkeys. It furthermore added tons of new files to /proc with all the ugliness of writable proc files, and it didn't conform to the coding style at all.
Matthew Garrett was extremely helpful with his fast review, and I have just sent the 0.94 version to linux-acpi, hopefully the last one before kernel inclusion. I should have done this a long time ago, but it just didn't feel right to go ahead without the original author's opinion. However, the driver now doesn't really look like the old driver anymore, very little code left. So I feel like I have more moral right to go ahead with it now...
Of course I've only tested it on the CF-R5. Anyone with different Let's note models and versions: Please feel welcome to test it and send bug and success reports.