We start with the Arch Wiki docs: https://wiki.archlinux.org/title/Kernel/Arch_build_system

Basics:

pacman -S devtools base-devel pacman-contrib

mkdir ~/build
cd ~/build

pkgctl repo clone --protocol=https linux

Modify the name:

vi linux/PKGBUILD

# change to custom
pkgbase=linux-custom

# remove $pkgbase-docs
pkgname=("$pkgbase" "$pkgbase-headers")

# add your patch to source
source= (
	...
	lhl-nvme.patch # this is the root linux/ folder
)

# run this after editing config
updpkgsums

Be sure to make your patches. This was a bit of a bear for me, the directsion https://wiki.archlinux.org/title/Kernel/Arch_build_system#Updating weren’t quite right, so I just sort of winged it. Ran a diff separately and then made sure the paths were correct.

❯ more lhl-nvme.patch 
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3ec38e2b9173..ab2583cb42aa 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2409,6 +2409,8 @@
 		timeout = NVME_CAP_TIMEOUT(ctrl->cap);
 	}
 
+  dev_info(ctrl->device, "[PATCH] nvme core got timeout %u\n",timeout);
+
 	ctrl->ctrl_config |= (NVME_CTRL_PAGE_SHIFT - 12) << NVME_CC_MPS_SHIFT;
 	ctrl->ctrl_config |= NVME_CC_AMS_RR | NVME_CC_SHN_NONE;
 	ctrl->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
@@ -2421,12 +2423,14 @@
 	if (ret)
 		return ret;
 
+  dev_info(ctrl->device, "[PATCH] nvme_wait_ready now wait for %u, previously %u\n",(timeout + 1) * 2, (timeout + 1)/2);
+
 	ctrl->ctrl_config |= NVME_CC_ENABLE;
 	ret = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
 	if (ret)
 		return ret;
 	return nvme_wait_ready(ctrl, NVME_CSTS_RDY, NVME_CSTS_RDY,
-			       (timeout + 1) / 2, "initialisation");
+			       (timeout + 1) * 2, "initialisation");
 }
 EXPORT_SYMBOL_GPL(nvme_enable_ctrl);

I needed to compile a custom kernel for a new system that is using a MAXIO MAP1602 controller that doesn’t reliably detect on boot.

This is sadly still not fixed in 6.5.0:

Faster Kernels

Using modprobed-db to compile only used kernel modules: https://wiki.archlinux.org/title/Modprobed-db

mount all filesystems
insert all removable media
attach all devices
encryption
qemu
sensors

Run modprobed-db store or enable the modprobed-db.service

Also add:

cifs
efivarfs
ext4
fat
isofs
loop
usbhid
usb_storage
vfat

The use make localmodconfig in PKGBUILD:

make LSMOD=$HOME/.config/modprobed.db localmodconfig

Speedup https://wiki.archlinux.org/title/Modprobed-db#Benefits_of_modprobed-db_with_%22make_localmodconfig%22_in_custom_kernels

mostlyobvious

Explorer

Compiling a Custom Arch Linux Kernel

Faster Kernels