Simple Rust driver that touches real hardware: PR 1/5 #270
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| // SPDX-License-Identifier: GPL-2.0+ | ||
| /* | ||
| * Copyright (C) 2017 Stefan Wahren <stefan.wahren@i2se.com> | ||
| */ |
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Perhaps add a comment here explaining that this is copied from from the version without -rust and highlighting the difference (bcm2835-rng-rust)?
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@wedsonaf the devicetrees are forked temporarily, until the platdev can bind to a devicetree compatible string. Which will be in PR 2/5.
In other words, these forked devicetrees will be "history" in the next PR. I'm sorry that I didn't indicate this anywhere !
In that light, do you still feel it's worth writing/reviewing the devicetree comments? If so I'll add them, no problem.
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Thanks for the clarification. No need for additional comments.
| license: b"GPL v2", | ||
| } | ||
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| struct RngModule { |
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For drivers that just register support for a platform device in their init function, we should provide a macro similar to C's module_platform_driver. I did that for miscdev in https://github.com/Rust-for-Linux/linux/blob/rust/rust/module.rs#L806.
This could perhaps be done in a different PR but I think it's important for us to provide this so that we reduce boilerplate code in Rust drivers, especially because their C counterparts already have such macros.
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Very good point !
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Can we defer this to the PR that adds probe()? We don't have a Trait object yet to pass to the macro.
Implements the bare minimum required to register a platform device
with the kernel. Registered devices won't actually be able to do
anything.
Registered platform devices will be visible in sysfs, under
/sys/bus/platform/{devices,drivers}/
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Implements the bare minimum for a platform driver to register itself with the core. It won't be able to do anything, except show up in sysfs. Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Provide a forked `defconfig` and devicetree, so the platform device core and driver can be easily tested on QEMU, or a Raspberri Pi Zero. Although called "bcm2835-rng-rust", this is not a functional hwrng driver, just a bare minimum platform_device. All it will do is log a message to dmesg: [ ] rust_kernel: Rust platform_device probed and show up in sysfs: /sys/bus/platform/driver/bcm2835-rng-rust/ (the driver) /sys/bus/platform/devices/bcm2835-rng-rust/ (the device) How to run on QEMU ================== Download a Raspbian image. I used `2021-03-04-raspios-buster-armhf-lite.img`. It will consist of two partitions. Discover their offsets using: ```sh $ fdisk -l 2021-03-04-raspios-buster-armhf-lite.img Device Boot Start End Sectors Size Id Type 2021-03-04-raspios-buster-armhf-lite.img1 8192 532479 524288 256M c W95 FAT32 (LBA) 2021-03-04-raspios-buster-armhf-lite.img2 532480 3645439 3112960 1.5G 83 Linux ``` Mount the second partition on your PC: (note how the offset is multiplied by 512) ```sh $ mount -o loop,offset=$((512*532480)) 2021-03-04-raspios-buster-armhf-lite.img /mnt Comment out everything in /etc/ld.so.preload - otherwise the Raspbian rootfs cannot support a mainline kernel: $ vi /etc/ld.so.preload # comment everything out $ umount /mnt ``` Build the kernel for arm 32-bit: ```sh $ make bcm2835_rust_defconfig # defconfig forked so `bcm2835-rng-rust` binds to our driver $ make zImage dtbs modules ``` Start QEMU: ```sh # to boot mainline, make sure that /etc/ld.so.preload is commented out # in the Raspbian image. qemu-system-arm \ -M raspi2 \ -append "rw earlyprintk loglevel=8 console=ttyAMA0,115200 dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2 rootwait" \ -cpu arm1176 \ -dtb bcm2836-rpi-2-b-rust.dts \ -hda ./2021-03-04-raspios-buster-armhf-lite.img \ -kernel zImage \ -m 1G \ -smp 4 \ -nographic \ ; How to run on a Raspberry Pi Zero(W) ==================================== Follow the instructions for QEMU above. Deploy the Raspbian image to SD card. Copy zImage and bcm2835-rpi-zero-w-rust.dtb to Raspbian's first (boot) partition: ``` zImage -> boot partition: kernel.img bcm2835-rpi-zero-w-rust.dtb -> boot partition: bcm2708-rpi-0-w.dtb ``` If you'd like wifi to keep working, also copy the kernel modules you built to Raspbian's second partition: ```sh $ make modules_install INSTALL_MOD_PATH=<somewhere> $ cp -rfa <somewhere> <Raspbian Partition> # should end up in /lib/modules/5.12.0-rc4+/ ``` Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
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v1 -> v2ojeda:
v3 to follow depending on wedsonaf's feedback. |
Simple Rust driver that touches real h/w: step 1 of 5
@alex and @ojeda suggested that #254 should be split into smaller PRs, so they can be reviewed and merged individually.
Roadmap: