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[PATCH RFC 0/3] media: videobuf2: opt-in dma_resv producer fences for V4L2 dmabuf exports

by Markus Fritsche

Hi, This series proposes a small opt-in API in videobuf2-core that lets V4L2 drivers populate a dma_resv exclusive write fence on the dmabufs they export to userspace, signalled when the buffer transitions to VB2_BUF_STATE_DONE. Two example drivers (hantro, rockchip-rga) opt in to demonstrate the call shape; the change is no-op for every other driver. Why --- Modern Wayland compositors and any other userspace consumers that import V4L2-produced dmabufs and want to do implicit synchronization the spec-clean way (poll(POLLIN) on the dmabuf fd, or DMA_BUF_IOCTL_EXPORT_SYNC_FILE for a sync_file) currently get either: 1. A stub fence from dma_buf_export_sync_file(), because the dmabuf's dma_resv has no fences populated. The kernel substitutes dma_fence_get_stub() which is permanently signalled. The compositor "successfully" waits on a fence that represents nothing real about the producer's state. 2. A poll(POLLIN) on the dmabuf fd that returns immediately for the same reason — dma_buf_poll_add_cb finds zero fences in the resv, triggers the wake callback inline, and reports POLLIN ready before the producer has actually said anything. Today this works as a happy accident on most paths because clients attach buffers after VIDIOC_DQBUF, which the userspace V4L2 contract guarantees only returns a buffer after the producer is done. So the implicit "the kernel's stub fence is fine because the buffer is already complete by the time anyone polls it" assumption has held. But: - It's a contract gap. The kernel claims to expose implicit sync; it does not, for V4L2 producers. - It paid latency for nothing. Every Wayland frame from a V4L2 producer pays a DMA_BUF_IOCTL_EXPORT_SYNC_FILE round-trip for a fence that's stub-signalled. On Mali-class hardware (RK3566 Wayland chrome video playback), this contributed to compositor stalls. Removing the wait at the compositor level is a workaround, not a fix. - It blocks downstream consumers from doing the right thing. A Wayland compositor that defensively waits on a sync_file gets a stub-fence pass-through with no actual gating; if the V4L2 driver ever has an out-of-band path that releases the buffer before finishing the write, there is no fence to gate on. What ---- Patch 1 adds: - struct dma_fence *release_fence to struct vb2_buffer - u64 dma_resv_fence_context + atomic64_t dma_resv_fence_seqno + spinlock_t dma_resv_fence_lock to struct vb2_queue - vb2_buffer_attach_release_fence(vb) — drivers call this from their buf_queue callback. Allocates a dma_fence on the queue's fence context, attaches it as DMA_RESV_USAGE_WRITE on each plane's dmabuf->resv. No-op for buffers without exported dmabufs. - vb2_buffer_done() extended to signal+put the fence if attached, so the producer's completion signal lands in the resv synchronously with the userspace DQBUF wakeup. Patches 2 and 3 add a single call to the helper from hantro_buf_queue and rga_buf_queue respectively. Both are demonstration drivers; other vb2 drivers can opt in incrementally with the same one-line change. Tested on --------- PineTab2 (RK3566 / Mali-G52 panfrost / mainline 6.19.10, this series backported), playing 1080p30 H.264 in chromium under KDE Plasma 6.6.4 Wayland. The test harness is the chromium-fourier patch series at https://github.com/marfrit/fourier — chromium plus a KWin patch that *previously bypassed* Transaction::watchDmaBuf because the kernel-side fence was stub-signalled. With this series applied, the bypass becomes unnecessary; KWin's fence wait completes correctly because the fence now signals when hantro completes the capture buffer write. End-to-end result before the kernel patch (chromium + Qt 6 patches + KWin watchDmaBuf bypass): 1080p30 H.264 plays through, ~81% combined chrome CPU, but the watchDmaBuf bypass weakens KWin's defenses against misbehaving clients. End-to-end result after the kernel patch (chromium + Qt 6 patches + plain unmodified KWin): 1080p30 H.264 plays through with the same CPU profile, KWin's watchDmaBuf wait completes within microseconds against the now-real producer fence, no defenses weakened. What's missing in this RFC -------------------------- - Other vb2-using drivers don't opt in. Each maintainer should look at their driver and decide. The hantro + rga patches show the shape; copying it to other drivers should be straightforward. - For drivers that have intermediate image-processor stages (e.g. CSI -> ISP -> user), the fence semantics across stage boundaries are out of scope here. This series only addresses the producer-to- userspace edge. - No selftest. videobuf2 doesn't have a great in-tree selftest harness for dmabuf flows; the validation is end-to-end at the userspace consumer level (KWin, in our case). Reviews especially welcome on: - The decision to make this opt-in per driver vs. automatic for all vb2-CAPTURE queues. Auto-on would force every driver to be audited; opt-in is incremental and safer but leaves the contract gap for drivers nobody touches. - Whether vb2_buffer_done is the right place to signal vs. an earlier hook (e.g. immediately after DMA-from-device finishes). For hantro the two are effectively the same; for drivers with asynchronous post-processing they may differ. - The choice of DMA_RESV_USAGE_WRITE — we are emitting the producer's write completion, so WRITE matches dma-buf documentation, but a sanity check is welcome. Cheers, Markus Markus Fritsche (3): media: videobuf2: add dma_resv release-fence helper media: hantro: attach dma_resv release fence at buf_queue media: rockchip-rga: attach dma_resv release fence at buf_queue .../media/common/videobuf2/videobuf2-core.c | 95 +++++++++++++++++++ drivers/media/platform/rockchip/rga/rga-buf.c | 10 ++ .../media/platform/verisilicon/hantro_v4l2.c | 12 +++ include/media/videobuf2-core.h | 29 ++++++ 4 files changed, 146 insertions(+) -- 2.47.3

1 month, 1 week

Living a Thousand Lives: Exploring the Quirky World of BitLife

by vast.stoat.yach＠hidingmail.net

Have you ever wondered what your life would look like if you made entirely different choices? Life simulation games have always been a fascinating genre for gamers, but few capture the unpredictable, hilarious, and sometimes chaotic nature of existence quite like Bitlife. Instead of relying on heavy 3D graphics, it is a text-based simulator that focuses entirely on the ripple effects of your decisions. It’s perfect for casual gaming sessions, so let's dive into how to play and get the most out of this quirky experience. https://bitlifefree.io/ Gameplay: Growing Up, One Year at a Time The premise of the game is incredibly simple but highly addictive. You are born with a random set of basic stats—Happiness, Health, Smarts, and Looks—in a random country to random parents. From there, you control your character's life year by year simply by tapping the "Age" button. In your early years, your choices are understandably limited to things like interacting with your parents, going to the doctor, or playing with pets. But as you grow into a teenager and an adult, the world completely opens up. You can choose to study hard, drop out, date, travel the world, buy real estate, or even turn to a life of crime. Every year, the game throws random scenarios at you: a classmate might insult you, you might be offered a questionable substance at a party, or you might find a wallet on the street. How you react directly impacts your stats and future opportunities. You might even have to pass mini-games, like navigating a maze for your driving test or escaping from prison. The ultimate goal is simply to live your life until your character passes away, leaving behind a unique legacy and a tombstone summarizing your deeds. Tips for a Great Experience If you are just starting out, here are a few tips to make your virtual life more successful—or at least more entertaining: Keep an eye on your core stats: Your Health and Happiness are crucial. If they drop too low, your character might face early health issues. Go to the gym, meditate, go to the movies, or spend time with family to keep these bars in the green. Education pays off (usually): If you want a high-paying, stable career like a doctor, judge, or CEO, use the "Study harder" option every year during school. Read books at the library to passively boost your Smarts stat. Hunt for Ribbons: At the end of every life, you are awarded a ribbon based on how you lived (e.g., "Hero," "Scandalous," "Lazy," or "Rich"). Trying to collect all the different ribbons is a great way to give yourself specific goals. Don't be afraid of the absurd: The real charm of the game is in its wild unpredictability. Sometimes, making terrible choices, trying to become a famous actor, or buying a crazy exotic pet leads to the most memorable playthroughs. Don't always play it safe! Conclusion Ultimately, the beauty of this simulator lies in its endless replayability. Every time you hit the button to start a new life, it is a completely blank slate. You can be a saint in one lifetime and an absolute menace to society in the next. Whether you have five minutes to kill on a bus commute or an hour to craft a sprawling, multi-generational family dynasty, diving into Bitlife offers a fun, lighthearted escape into a world where you pull all the strings. Give it a try, and see exactly where your choices take you!

1 month, 1 week

Bake Your Way to Billions: A Look at the Addictive World of Store Management Games

by hot.meerkat.lloh＠hidingmail.net

Ever dreamed of running your own bustling enterprise, watching your profits soar, and building an empire from humble beginnings? If so, you've likely stumbled upon the fascinating and surprisingly addictive world of store management games. These titles offer a unique blend of strategy, incremental growth, and the satisfying feeling of seeing your hard work pay off. And when it comes to the purest, most delightful form of this genre, one game stands out: https://cookieclickers.io/ The Sweet Simplicity of Cookie Clicker: A Gateway to Management At its heart, Cookie Clicker is incredibly simple. You start with a single, humble cookie, and your goal is to click it to generate more cookies. These initial clicks are crucial, as they fund your first upgrades. Soon, you’ll be able to purchase "grandmas," who automatically bake cookies for you, freeing up your clicking finger. From there, the sky's the limit! You'll acquire farms, factories, mines, and even portals to other dimensions, all dedicated to the singular purpose of baking more and more cookies. What makes Cookie Clicker so captivating is its elegant progression system. Each new upgrade and building provides a tangible boost to your cookie production, creating a satisfying feedback loop. The numbers on your screen grow exponentially, transforming from humble dozens to mind-boggling septillions and beyond. It’s a masterclass in incremental design, making every new purchase feel impactful and exciting. Beyond the Click: Strategic Thinking and Exponential Growth While the initial appeal of Cookie Clicker might be the simple act of clicking, true mastery lies in strategic decision-making. As your cookie empire expands, you'll be faced with choices: Upgrade Prioritization: Should you invest in another Grandma, a new farm, or a powerful upgrade that boosts all your existing structures? Understanding the cost-benefit analysis of each option is key. Synergies: Many upgrades have synergistic effects, meaning they become more powerful when paired with specific buildings. Discovering these combinations is a delightful puzzle. Ascension and Prestige: Eventually, you’ll unlock the ability to “ascend,” resetting your game but granting you powerful "heavenly chips" that provide permanent bonuses. This meta-progression adds a whole new layer of long-term strategy, encouraging you to rethink your approach with each new playthrough. These elements elevate Cookie Clicker from a simple clicking game to a genuinely engaging management simulation. It teaches you about exponential growth, compound interest (in a fun, cookie-filled way!), and the satisfaction of building something from nothing. Tips for Aspiring Cookie Tycoons If you’re ready to dive into the sweet, sweet world of Cookie Clicker, here are a few friendly tips to get you started: Don't Be Afraid to Click! In the early game, your clicks are your most valuable resource. Keep that finger moving! Invest in Grandmas Early: They're your first step towards automation and a steady cookie income. Always Buy Upgrades: The small boosts they provide add up quickly and are often more cost-effective than new buildings in the short term. Look for Golden Cookies: These appear randomly and offer temporary, powerful buffs. Clicking them can drastically boost your production! Consider Ascending: While it seems daunting to reset your progress, the permanent bonuses you gain make future runs much faster and more efficient. The Endless Appeal of Automation Cookie Clicker, and store management games in general, tap into a fundamental human desire: the joy of creation and the satisfaction of watching systems work efficiently. There's a particular kind of quiet pleasure in setting up a well-oiled machine and observing its output multiply. So, if you're looking for a game that's easy to pick up, surprisingly deep, and immensely satisfying, give Cookie Clicker a try. You might just find yourself baking billions before you know it!

1 month, 1 week

[PATCH v2] dma-buf: heaps: use max3() in dma_heap_ioctl

by Thorsten Blum

Replace two nested max() calls with a single max3() in dma_heap_ioctl(). Reviewed-by: T.J. Mercier <tjmercier(a)google.com> Signed-off-by: Thorsten Blum <thorsten.blum(a)linux.dev> --- Changes in v2: - Include minmax.h as suggested by T.J. Mercier - v1: https://lore.kernel.org/lkml/20260427172519.417333-3-thorsten.blum@linux.de… --- drivers/dma-buf/dma-heap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index ac5f8685a649..d49188893608 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -13,6 +13,7 @@ #include <linux/err.h> #include <linux/export.h> #include <linux/list.h> +#include <linux/minmax.h> #include <linux/nospec.h> #include <linux/syscalls.h> #include <linux/uaccess.h> @@ -153,7 +154,7 @@ static long dma_heap_ioctl(struct file *file, unsigned int ucmd, in_size = 0; if ((ucmd & kcmd & IOC_OUT) == 0) out_size = 0; - ksize = max(max(in_size, out_size), drv_size); + ksize = max3(in_size, out_size, drv_size); /* If necessary, allocate buffer for ioctl argument */ if (ksize > sizeof(stack_kdata)) {

1 month, 1 week

[PATCH] dma-buf: heaps: use max3() in dma_heap_ioctl

by Thorsten Blum

Replace two nested max() calls with a single max3() in dma_heap_ioctl(). Signed-off-by: Thorsten Blum <thorsten.blum(a)linux.dev> --- drivers/dma-buf/dma-heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index ac5f8685a649..52eec2ebb2e8 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -153,7 +153,7 @@ static long dma_heap_ioctl(struct file *file, unsigned int ucmd, in_size = 0; if ((ucmd & kcmd & IOC_OUT) == 0) out_size = 0; - ksize = max(max(in_size, out_size), drv_size); + ksize = max3(in_size, out_size, drv_size); /* If necessary, allocate buffer for ioctl argument */ if (ksize > sizeof(stack_kdata)) {

1 month, 1 week

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1 month, 1 week

[PATCH V13 0/7] Rust support for powerpc

by Mukesh Kumar Chaurasiya (IBM)

Enable experimental rust support for ppc64le and ppc32be. The patch for ppc32 has been provided by Link Mauve[1] and ppc64le support[2] has been merged over it. ppc32 needs some toolchain fixes mentioned in the patch `rust: Add PowerPC support` and the discussion for that is done here[1]. This has been tested on - powernv9 hardware - pseries P11 hardware - pseries(9, 10) qemu - powernv(9, 10) qemu - rustdoc on x86 and powerpc64le - rusttest on x86 and powerpc64le We are actively working with our LLVM team to get the target for ppc, ppc64 and ppc64le in the rust compiler. [1] https://lore.kernel.org/all/20260204030507.8203-1-linkmauve@linkmauve.fr [2] https://lore.kernel.org/all/20260204042417.83903-1-mkchauras@gmail.com Changelog: V12 -> V13: - Added a patch for fixing build issue on ppc32 by Link Mauve - Added another patch to fix a build issue in dma-buf - Added another patch to enforce minimum `rustc` version for powerpc V12: https://lore.kernel.org/all/20260421120958.190430-1-mkchauras@gmail.com/ V11 -> V12: - Rebased to mainline (rust/Makefile conflict resolved) V11: https://lore.kernel.org/all/20260417152253.2312961-1-mkchauras@gmail.com/ V10 -> V11: - Updated `rust/Makefile` - Not all libraries are move to `rust/host` directory now. Only proc_macro2, quote and syn are moved - Special handling for pin init is added. Details in commit - Removed mkdir for `rust/host`, this is now handled by toolchain. V10: https://lore.kernel.org/all/20260406200149.3727922-1-mkchauras@gmail.com/ V9 -> V10: - rust/Makefile updated with review comments from Miguel - Patch 1/4 updated with commit message and subject V9: https://lore.kernel.org/all/20260404121610.1956528-1-mkchauras@gmail.com/ V8 -> V9: - rust/Makefile updated with a directory instead of abspath V8: https://lore.kernel.org/all/20260403145308.1042622-1-mkchauras@gmail.com/ V7 -> V8: - rust/Makefile updated to separate host libraries from target V7: https://lore.kernel.org/all/20260329160254.2592207-1-mkchauras@gmail.com/ Changelog: V6 -> V7: - Documentation removed as powerpc is still under development - Added a fix for race condition in rust/Makefile V6: https://lore.kernel.org/all/20260210090023.2587534-1-mkchauras@gmail.com V5 -> V6: - Added a missing Tested by from Venkat which got missed since V3 - Support is marked as Maintained instead of experimental V5: https://lore.kernel.org/all/20260210053756.2088302-1-mkchauras@gmail.com V4 -> V5: - Removed a nested ifdef from PPC64 for Little endian toolchain V4: https://lore.kernel.org/all/20260209105456.1551677-1-mkchauras@gmail.com V3 -> V4: - Co-developed-by header added in patch 1 V3: https://lore.kernel.org/all/20260205180429.3280657-1-mkchauras@gmail.com V2 -> V3: - Splited HAVE_RUST in 2 lines - BINDGEN_TARGET_powerpc initialized before assigning the same to BINDGEN_TARGET V2: https://lore.kernel.org/all/20260204210125.613350-1-mkchauras@gmail.com V1 -> V2: - jump label fix for rust has been moved to a separate patch - PPC32 support has been taken - rust support has been marked experimental - target.json dependency has been removed - HAVE_RUST now depends on CPU_LITTLE_ENDIAN for PPC64 Link Mauve (2): rust: Make __udivdi3() and __umoddi3() panic rust: Add PowerPC support Mukesh Kumar Chaurasiya (IBM) (5): rust: Fix "multiple candidates for rmeta dependency core" error dma-resv: Fix undefined symbol when CONFIG_DMA_SHARED_BUFFER is disabled powerpc/jump_label: adjust inline asm to be consistent rust/powerpc: Set min rustc version for powerpc powerpc: Enable Rust for ppc64le arch/powerpc/Kconfig | 2 ++ arch/powerpc/Makefile | 7 ++++ arch/powerpc/include/asm/jump_label.h | 23 ++++++------ include/linux/dma-resv.h | 2 +- rust/Makefile | 52 +++++++++++++++++---------- rust/compiler_builtins.rs | 6 ++++ scripts/min-tool-version.sh | 6 +++- 7 files changed, 68 insertions(+), 30 deletions(-) -- 2.53.0

1 month, 1 week

[PATCH v12 0/5] Rust bindings for gem shmem

by Lyude Paul

Most of this patch series has already been pushed upstream, this is just the second half of the patch series that has not been pushed yet + some additional changes which were required to implement changes requested by the mailing list. This patch series is originally from Asahi, previously posted by Daniel Almeida. The previous version of the patch series can be found here: https://patchwork.freedesktop.org/series/164580/ Branch with patches applied available here sure this builds: https://gitlab.freedesktop.org/lyudess/linux/-/commits/rust/gem-shmem This patch series applies on top of drm-rust-next Lyude Paul (5): rust: drm: gem: s/device::Device/Device/ for shmem.rs drm/gem/shmem: Introduce __drm_gem_shmem_free_sgt_locked() drm/gem/shmem: Export drm_gem_shmem_get_pages_sgt_locked() rust: drm: gem: Introduce shmem::SGTable rust: drm: gem: Add vmap functions to shmem bindings drivers/gpu/drm/drm_gem_shmem_helper.c | 48 ++- include/drm/drm_gem_shmem_helper.h | 2 + rust/kernel/drm/gem/shmem.rs | 557 ++++++++++++++++++++++++- 3 files changed, 593 insertions(+), 14 deletions(-) base-commit: a7a080bb4236ebe577b6776d940d1717912ff6dd -- 2.53.0

1 month, 2 weeks

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