Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] drm: sleeping in atomic context in plane and CRTC callbacks - [Medium] drm/trigger5: deferred display damage is never flushed if userspace goes idle --
commit 12d04056078c58dc5db832cf84f326c797a58e7c Author: Ho Jie Feng <[email protected]> drm/trigger5: Add MCT Trigger 5 USB display driver This commit introduces a new DRM driver for MCT Trigger 5 USB display adapters. It implements modesetting, USB framebuffer updates, connector detection, and EDID retrieval based on reverse-engineered protocols. > diff --git a/drivers/gpu/drm/tiny/trigger5.c b/drivers/gpu/drm/tiny/trigger5.c > new file mode 100644 > index 0000000000000..d0ab06bab8d73 > --- /dev/null > +++ b/drivers/gpu/drm/tiny/trigger5.c [ ... ] > +static void trigger5_transfer_work(struct work_struct *work) > +{ [ ... ] > + if (transfer->sgr.status) > + drm_err_ratelimited(&trigger5->drm, > + "USB transfer failed: %d\n", > + transfer->sgr.status); > + else if (transfer->sgr.bytes != transfer->frame_len) > + drm_err_ratelimited(&trigger5->drm, > + "short USB transfer: %zu/%zu bytes\n", > + transfer->sgr.bytes, transfer->frame_len); > + else if (READ_ONCE(trigger5->display_enabled)) > + /* Keepalive must only be sent after a frame has been sent */ > + queue_delayed_work(trigger5->transfer_wq, > + &trigger5->keepalive_work, > + > msecs_to_jiffies(TRIGGER5_KEEPALIVE_INTERVAL_MS)); > + > +exit: > + drm_dev_exit(idx); > +complete: > + complete(&transfer->frame_complete); > +} [Severity: Medium] Does this transfer completion need to check for or schedule any work to handle damage deferred in pending_rect? If userspace stops sending new frames (e.g., when the system goes idle), the deferred damage might never get flushed to the screen. [ ... ] > +static void trigger5_crtc_atomic_enable(struct drm_crtc *crtc, > + struct drm_atomic_commit *state) > +{ [ ... ] > + trigger5_stop_io(trigger5); > + > + /* Sequence recovered from USB captures. */ > + ret = usb_control_msg_recv(udev, 0, > + TRIGGER5_REQUEST_FIRMWARE_RESET, > + USB_DIR_IN | USB_TYPE_VENDOR | > + USB_RECIP_DEVICE, > + 0x0000, 0x0000, data, 1, > + USB_CTRL_GET_TIMEOUT, GFP_KERNEL); [Severity: High] Is it safe to use GFP_KERNEL and blocking USB functions here? CRTC atomic enable callbacks are atomic context paths where sleeping is strictly forbidden. Calling blocking USB transfers with the GFP_KERNEL flag in this path violates DRM invariants and can cause kernel warnings or deadlocks. [ ... ] > +static void trigger5_crtc_atomic_disable(struct drm_crtc *crtc, > + struct drm_atomic_commit *state) > +{ [ ... ] > + trigger5_stop_io(trigger5); > + > + ret = usb_control_msg_recv(udev, 0, > + TRIGGER5_REQUEST_FIRMWARE_RESET, > + USB_DIR_IN | USB_TYPE_VENDOR | > + USB_RECIP_DEVICE, > + 0x0001, 0x0000, &data, 1, > + USB_CTRL_GET_TIMEOUT, GFP_KERNEL); [Severity: High] Similarly to the atomic enable callback, is it safe to use a blocking USB function with GFP_KERNEL allocation here? CRTC atomic disable callbacks are also atomic contexts where sleeping is prohibited. [ ... ] > +static void trigger5_plane_atomic_update(struct drm_plane *plane, > + struct drm_atomic_commit *atomic_state) > +{ [ ... ] > + /* > + * This should almost never wait because we have should have a > + * pending transfer ready to be de-queued above in case the transfer > + * hasn't finished, but do a bounded wait just in case it gets stuck > + */ > + if (!wait_for_completion_timeout(¤t_transfer->frame_complete, > + msecs_to_jiffies(20))) > + goto exit_save_pending; [Severity: High] Can wait_for_completion_timeout() sleep in this context? Plane atomic update callbacks execute in atomic context where sleeping is forbidden. Blocking for up to 20ms here will cause system instability. [Severity: Medium] When this timeout occurs, the damage is saved to pending_rect, but no asynchronous flush is queued to present it later. As mentioned above in trigger5_transfer_work(), if the display update aborts here and userspace stops sending new frames, the screen might permanently display stale content. [ ... ] > + iosys_map_set_vaddr(&data_map, > + current_transfer->buf.data + sizeof(*header)); > + > + ret = drm_gem_fb_begin_cpu_access(state->fb, DMA_FROM_DEVICE); [Severity: High] Could this function acquire DMA reservation locks that might sleep? Since this is still within the plane atomic update callback, calling a function that can sleep violates the DRM atomic context rules. > + if (ret < 0) { > + complete(¤t_transfer->frame_complete); > + goto exit_save_pending; > + } > + > + drm_fb_xrgb8888_to_rgb888(&data_map, NULL, > + &shadow_plane_state->data[0], > + state->fb, ¤t_rect, > + &shadow_plane_state->fmtcnv_state); > + > + drm_gem_fb_end_cpu_access(state->fb, DMA_FROM_DEVICE); -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
