linux: enable PREEMPT_RT

This includes the real-time patch set and enables PREEMPT_RT.

linux-6.6.defconfig

@@ -4,7 +4,7 @@ CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
 CONFIG_NO_HZ=y
 CONFIG_HIGH_RES_TIMERS=y
-CONFIG_PREEMPT=y
+CONFIG_PREEMPT_RT=y
 CONFIG_IKCONFIG=y
 CONFIG_IKCONFIG_PROC=y
 CONFIG_MEMCG=y
@@ -15,11 +15,13 @@ CONFIG_CGROUP_FREEZER=y
 CONFIG_CPUSETS=y
 CONFIG_CGROUP_DEVICE=y
 CONFIG_CGROUP_CPUACCT=y
+CONFIG_NAMESPACES=y
 # CONFIG_UTS_NS is not set
 # CONFIG_IPC_NS is not set
 # CONFIG_PID_NS is not set
 # CONFIG_NET_NS is not set
 CONFIG_SCHED_AUTOGROUP=y
+CONFIG_EXPERT=y
 # CONFIG_PERF_EVENTS is not set
 CONFIG_PROFILING=y
 CONFIG_ARCH_BCM=y
@@ -267,9 +269,11 @@ CONFIG_REGULATOR_AD5398=m
 CONFIG_REGULATOR_GPIO=y
 CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY=m
 CONFIG_MEDIA_SUPPORT=m
+CONFIG_MEDIA_SUPPORT_FILTER=y
 CONFIG_MEDIA_CAMERA_SUPPORT=y
 CONFIG_MEDIA_PLATFORM_SUPPORT=y
 CONFIG_MEDIA_USB_SUPPORT=y
+CONFIG_V4L_PLATFORM_DRIVERS=y
 CONFIG_VIDEO_BCM2835_UNICAM=m
 CONFIG_VIDEO_RASPBERRYPI_PISP_BE=m
 CONFIG_VIDEO_IMX219=m
@@ -346,7 +350,6 @@ CONFIG_LEDS_TRIGGER_TIMER=y
 CONFIG_LEDS_TRIGGER_ONESHOT=y
 CONFIG_LEDS_TRIGGER_HEARTBEAT=y
 CONFIG_LEDS_TRIGGER_BACKLIGHT=y
-CONFIG_LEDS_TRIGGER_CPU=y
 CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
 CONFIG_LEDS_TRIGGER_TRANSIENT=y
 CONFIG_LEDS_TRIGGER_INPUT=y
@@ -404,3 +407,4 @@ CONFIG_DMA_CMA=y
 CONFIG_CMA_SIZE_MBYTES=5
 CONFIG_PRINTK_TIME=y
 CONFIG_PANIC_TIMEOUT=10
+# CONFIG_FTRACE is not set

nerves_defconfig

@@ -29,7 +29,7 @@ BR2_ROOTFS_POST_IMAGE_SCRIPT="${NERVES_DEFCONFIG_DIR}/post-createfs.sh"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
 BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION="https://github.com/raspberrypi/linux/archive/refs/tags/stable_20241008.tar.gz"
-BR2_LINUX_KERNEL_PATCH="${NERVES_DEFCONFIG_DIR}/linux"
+BR2_LINUX_KERNEL_PATCH="http://cdn.kernel.org/pub/linux/kernel/projects/rt/6.6/patch-6.6.53-rt44.patch.gz ${NERVES_DEFCONFIG_DIR}/linux"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="${NERVES_DEFCONFIG_DIR}/linux-6.6.defconfig"
 BR2_LINUX_KERNEL_XZ=y