On Fri, Feb 25, 2022 at 05:06:32PM +0100, Benjamin Tissoires wrote: > On Thu, Feb 24, 2022 at 6:21 PM Yonghong Song <yhs@xxxxxx> wrote: > > > > > > > > On 2/24/22 5:49 AM, Benjamin Tissoires wrote: > > > Hi Greg, > > > > > > Thanks for the quick answer :) > > > > > > On Thu, Feb 24, 2022 at 12:31 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > >> > > >> On Thu, Feb 24, 2022 at 12:08:22PM +0100, Benjamin Tissoires wrote: > > >>> Hi there, > > >>> > > >>> This series introduces support of eBPF for HID devices. > > >>> > > >>> I have several use cases where eBPF could be interesting for those > > >>> input devices: > > >>> > > >>> - simple fixup of report descriptor: > > >>> > > >>> In the HID tree, we have half of the drivers that are "simple" and > > >>> that just fix one key or one byte in the report descriptor. > > >>> Currently, for users of such devices, the process of fixing them > > >>> is long and painful. > > >>> With eBPF, we could externalize those fixups in one external repo, > > >>> ship various CoRe bpf programs and have those programs loaded at boot > > >>> time without having to install a new kernel (and wait 6 months for the > > >>> fix to land in the distro kernel) > > >> > > >> Why would a distro update such an external repo faster than they update > > >> the kernel? Many sane distros update their kernel faster than other > > >> packages already, how about fixing your distro? :) > > > > > > Heh, I'm going to try to dodge the incoming rhel bullet :) > > > > > > It's true that thanks to the work of the stable folks we don't have to > > > wait 6 months for a fix to come in. However, I think having a single > > > file to drop in a directory would be easier for development/testing > > > (and distribution of that file between developers/testers) than > > > requiring people to recompile their kernel. > > > > > > Brain fart: is there any chance we could keep the validated bpf > > > programs in the kernel tree? > > > > Yes, see kernel/bpf/preload/iterators/iterators.bpf.c. > > Thanks. This is indeed interesting. > I am not sure the exact usage of it though :) > > One thing I wonder too while we are on this topic, is it possible to > load a bpf program from the kernel directly, in the same way we can > request firmwares? We used to be able to do that, putting bpf programs inside a module. But that might have gotten removed because no one actually used it. I thought it was a nice idea. > Because if we can do that, in my HID use case we could replace simple > drivers with bpf programs entirely and reduce the development cycle to > a bare minimum. How would the development cycle change? You could get rid of many in-kernel hid drivers and replace them with bpf code perhaps? Maybe that's a good use case :) thanks, greg k-h
