New version of the sleepable bpf_timer code, without BPF changes, as they can now go through the HID tree independantly:
https://lore.kernel.org/all/20240315-hid-bpf-sleepable-v4-0-5658f2540564@ker...
For reference, the use cases I have in mind:
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Basically, I need to be able to defer a HID-BPF program for the following reasons (from the aforementioned patch): 1. defer an event: Sometimes we receive an out of proximity event, but the device can not be trusted enough, and we need to ensure that we won't receive another one in the following n milliseconds. So we need to wait those n milliseconds, and eventually re-inject that event in the stack.
2. inject new events in reaction to one given event: We might want to transform one given event into several. This is the case for macro keys where a single key press is supposed to send a sequence of key presses. But this could also be used to patch a faulty behavior, if a device forgets to send a release event.
3. communicate with the device in reaction to one event: We might want to communicate back to the device after a given event. For example a device might send us an event saying that it came back from sleeping state and needs to be re-initialized.
Currently we can achieve that by keeping a userspace program around, raise a bpf event, and let that userspace program inject the events and commands. However, we are just keeping that program alive as a daemon for just scheduling commands. There is no logic in it, so it doesn't really justify an actual userspace wakeup. So a kernel workqueue seems simpler to handle.
bpf_timers are currently running in a soft IRQ context, this patch series implements a sleppable context for them.
Cheers, Benjamin
To: Jiri Kosina jikos@kernel.org To: Benjamin Tissoires benjamin.tissoires@redhat.com To: Jonathan Corbet corbet@lwn.net To: Shuah Khan shuah@kernel.org Cc: Benjamin Tissoires bentiss@kernel.org Cc: linux-input@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: bpf@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kselftest@vger.kernel.org
--- Changes in v4: - dropped the BPF changes, they can go independently in bpf-core - dropped the HID-BPF integration tests with the sleppable timers, I'll re-add them once both series (this and sleepable timers) are merged - Link to v3: https://lore.kernel.org/r/20240221-hid-bpf-sleepable-v3-0-1fb378ca6301@kerne...
Changes in v3: - fixed the crash from v2 - changed the API to have only BPF_F_TIMER_SLEEPABLE for bpf_timer_start() - split the new kfuncs/verifier patch into several sub-patches, for easier reviews - Link to v2: https://lore.kernel.org/r/20240214-hid-bpf-sleepable-v2-0-5756b054724d@kerne...
Changes in v2: - make use of bpf_timer (and dropped the custom HID handling) - implemented bpf_timer_set_sleepable_cb as a kfunc - still not implemented global subprogs - no sleepable bpf_timer selftests yet - Link to v1: https://lore.kernel.org/r/20240209-hid-bpf-sleepable-v1-0-4cc895b5adbd@kerne...
--- Benjamin Tissoires (7): HID: bpf/dispatch: regroup kfuncs definitions HID: bpf: export hid_hw_output_report as a BPF kfunc selftests/hid: add KASAN to the VM tests selftests/hid: Add test for hid_bpf_hw_output_report HID: bpf: allow to inject HID event from BPF selftests/hid: add tests for hid_bpf_input_report HID: bpf: allow to use bpf_timer_set_sleepable_cb() in tracing callbacks.
Documentation/hid/hid-bpf.rst | 2 +- drivers/hid/bpf/hid_bpf_dispatch.c | 226 ++++++++++++++------- drivers/hid/hid-core.c | 2 + include/linux/hid_bpf.h | 3 + tools/testing/selftests/hid/config.common | 1 + tools/testing/selftests/hid/hid_bpf.c | 112 +++++++++- tools/testing/selftests/hid/progs/hid.c | 46 +++++ .../testing/selftests/hid/progs/hid_bpf_helpers.h | 6 + 8 files changed, 324 insertions(+), 74 deletions(-) --- base-commit: 3e78a6c0d3e02e4cf881dc84c5127e9990f939d6 change-id: 20240314-b4-hid-bpf-new-funcs-ecf05d0ef870
Best regards,