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AJvYcCWgtP5zNmOzsvgPZGUQzut+r1k2Er5oUf83KBpqMGVG4DzUSAQx0YrfkhO31m9spMFa56YRcwrd@lists.linux.dev X-Gm-Message-State: AOJu0Yzo+9OEZHqcgfYgEOSpjGlhrpY1+BQDwzrbSd4fgVuKgP/0sQyL U2k6wSXO0yj4CBgn2vObX0sMqgoeNccYtlmCH8nSebqxNbVpAVcqmyRSpoI2uAgvV1It9lzt0g4 jMgHar4FOiNZ5Do3979uebpxphppkTWNB X-Gm-Gg: ASbGnctiFNOvoWBAaG60rjrdAbmjhHoRBPSPylOyErM/Urnn58zDrF8hit682r4wG2R G5igDdTb8Xd9ylNZWIDXKwXPrwe8cNYrDWA1K1QVw93ZcGKDpuf20GIHne6Ph9tH2Dd4Sp1UzEG ouQb0qH4NphXvL X-Google-Smtp-Source: AGHT+IHkfgnrV+BJNL4baF5nekJSwGBo3ZopJ8YNhxStsP2Hf7g6+UzEp276HXeTQtpo/E5x2POhhtXsLL4/gCTqORA= X-Received: by 2002:adf:f3c9:0:b0:38f:2b59:3f78 with SMTP id ffacd0b85a97d-38f6f0ac5a3mr257914f8f.45.1740076844972; Thu, 20 Feb 2025 10:40:44 -0800 (PST) Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <45rpsr92-4416-9no4-8o26-r0998nr77nr8@xreary.bet> In-Reply-To: From: Alexei Starovoitov Date: Thu, 20 Feb 2025 10:40:32 -0800 X-Gm-Features: AWEUYZlQ2ngnBUpsPvZmt-IUjjrYChxu8xuPgnYSqjT2MUxJIeYsrj1qt7MyBZU Message-ID: Subject: Re: Rust kernel policy To: Christoph Hellwig Cc: Jiri Kosina , Miguel Ojeda , rust-for-linux , Linus Torvalds , Greg KH , David Airlie , LKML , ksummit@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Feb 19, 2025 at 10:33=E2=80=AFPM Christoph Hellwig wrote: > > On Tue, Feb 18, 2025 at 06:36:55PM +0100, Jiri Kosina wrote: > > > [2] The idea of drivers in eBPF as done by HID also really doesn't he= lp > > > with that as much as I like eBPF for some use cases > > > > I don't necessarily agree on this specific aspect, but what (at least t= o > > me personally) is the crucial point here -- if we at some point decide > > that HID-eBPF is somehow potentially unhealthy for the project / > > ecosystem, we can just drop it and convert the existing eBPF snippets t= o a > > proper simple HID bus drivers trivially (I'd even dare to say that to s= ome > > extent perhaps programatically). > > Well, Linus declared any bpf kfunc / helper program type change that > breaks userspace as a no-go. And such a change very much does. Have to chime in into this rust thread to correct the facts. See the doc: https://github.com/torvalds/linux/blob/master/Documentation/bpf/kfuncs.rst#= 3-kfunc-lifecycle-expectations TLDR: "A kfunc will never have any hard stability guarantees. BPF APIs cannot and will not ever hard-block a change in the kernel..." git log proves the history of changing/removing kfuncs. hid-bpf iself is another example of that policy. It was redesigned from one way of hooking into hid core to a completely different approach. It may happen again, if necessary.