intro
as you may know, I use an old ipad as a second screen.
in a nutshell, it relies on the evdi kernel module to create a virtual display which is then accessed by the ipad via a VNC Viewer.
pne quirk is that almost every time I update the kernel, evdi (and consequently my ipad setup) also breaks. I am not super familiar with kernel shenanigans so I don’t know if it’s a fundamental issue or not.
that being said, fixing it is relative fine as long as:
- a) there’s been a fix released
- b) I remember the steps on how to reinstall the module
for a), well, running fedora helps a bit with this (I reckon it would be much worse with a rolling release distro, like arch). It’s still possible to mess it up though, so I usually wait a few weeks before updating the OS version. Also watching new releases help.
now for b), that’s what this blog post is for. I usually maintain notes for almost everything technical I do, but it’s designed to be a write-intensive workflow (which means I suffer between greping for the right keywords and sequentially going over my daily notes).
the meat
i am going from kernel 5.15.8-200.fc35.x86_64 to 5.15.12-200.fc35.x86_64
last time I updated was 2021-12-19.
let’s clone the evdi repo and check out the devel branch, or in my case I already had it cloned
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| git@github.com:DisplayLink/evdi.git
git checkout devel
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pull latest changes
make it
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| ❯ make
CFLAGS="-isystem./include -isystem./include/uapi -Werror -Wextra -Wall -Wmissing-prototypes -Wstrict-prototypes -Wno-error=missing-field-initializers -Werror=sign-compare " make -C module
make[1]: Entering directory '/home/eduardo/projects/evdi/module'
make -C /lib/modules/5.15.12-200.fc35.x86_64/build M=$PWD
make[2]: Entering directory '/usr/src/kernels/5.15.12-200.fc35.x86_64'
CC [M] /home/eduardo/projects/evdi/module/evdi_platform_drv.o
CC [M] /home/eduardo/projects/evdi/module/evdi_platform_dev.o
CC [M] /home/eduardo/projects/evdi/module/evdi_sysfs.o
CC [M] /home/eduardo/projects/evdi/module/evdi_modeset.o
CC [M] /home/eduardo/projects/evdi/module/evdi_connector.o
CC [M] /home/eduardo/projects/evdi/module/evdi_encoder.o
CC [M] /home/eduardo/projects/evdi/module/evdi_drm_drv.o
CC [M] /home/eduardo/projects/evdi/module/evdi_fb.o
CC [M] /home/eduardo/projects/evdi/module/evdi_gem.o
CC [M] /home/eduardo/projects/evdi/module/evdi_painter.o
CC [M] /home/eduardo/projects/evdi/module/evdi_params.o
CC [M] /home/eduardo/projects/evdi/module/evdi_cursor.o
CC [M] /home/eduardo/projects/evdi/module/evdi_debug.o
CC [M] /home/eduardo/projects/evdi/module/evdi_i2c.o
CC [M] /home/eduardo/projects/evdi/module/evdi_ioc32.o
LD [M] /home/eduardo/projects/evdi/module/evdi.o
MODPOST /home/eduardo/projects/evdi/module/Module.symvers
CC [M] /home/eduardo/projects/evdi/module/evdi.mod.o
LD [M] /home/eduardo/projects/evdi/module/evdi.ko
BTF [M] /home/eduardo/projects/evdi/module/evdi.ko
Skipping BTF generation for /home/eduardo/projects/evdi/module/evdi.ko due to unavailability of vmlinux
make[2]: Leaving directory '/usr/src/kernels/5.15.12-200.fc35.x86_64'
make[1]: Leaving directory '/home/eduardo/projects/evdi/module'
CFLAGS="-I../module -Werror -Wextra -Wall -Wmissing-prototypes -Wstrict-prototypes -Wno-error=missing-field-initializers -Werror=sign-compare " make -C library
make[1]: Entering directory '/home/eduardo/projects/evdi/library'
cc evdi_lib.o -shared -Wl,-soname,libevdi.so.0 -o libevdi.so.1.10.0 -lc -lgcc
cp libevdi.so.1.10.0 libevdi.so
make[1]: Leaving directory '/home/eduardo/projects/evdi/library'
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make install it
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| sudo make install
make -C module install
make[1]: Entering directory '/home/eduardo/projects/evdi/module'
make -C /lib/modules/5.15.12-200.fc35.x86_64/build M=$PWD INSTALL_MOD_PATH= INSTALL_MOD_DIR=/kernel/drivers/gpu/drm/evdi modules_install
make[2]: Entering directory '/usr/src/kernels/5.15.12-200.fc35.x86_64'
INSTALL /lib/modules/5.15.12-200.fc35.x86_64//kernel/drivers/gpu/drm/evdi/evdi.ko
SIGN /lib/modules/5.15.12-200.fc35.x86_64//kernel/drivers/gpu/drm/evdi/evdi.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
DEPMOD /lib/modules/5.15.12-200.fc35.x86_64
make[2]: Leaving directory '/usr/src/kernels/5.15.12-200.fc35.x86_64'
true
make[1]: Leaving directory '/home/eduardo/projects/evdi/module'
make -C library install
make[1]: Entering directory '/home/eduardo/projects/evdi/library'
install -d /usr/local/lib
install -m 755 libevdi.so.1.10.0 /usr/local/lib/libevdi.so.1.10.0
ln -sf libevdi.so.1.10.0 /usr/local/lib/libevdi.so.0
ln -sf libevdi.so.0 /usr/local/lib/libevdi.so
make[1]: Leaving directory '/home/eduardo/projects/evdi/library'
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ok it failed due to a missing certs/signing_key.pem to sign the module. You need to generate one.
in my case I already had one, so I just copied from the previous kernel.
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| find /usr/src/kernels/ -name "*.pem"
/usr/src/kernels/5.15.8-200.fc35.x86_64/certs/signing_key.pem
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my kernel is
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| uname -r
5.15.12-200.fc35.x86_64
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copying
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| sudo cp -r /usr/src/kernels/5.13.14-200.fc34.x86_64/certs/ /usr/src/kernels/5.15.12-200.fc35.x86_64/
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you can use something like $(uname -r), but since I run fish the syntax is different and I don’t want to publish something with a syntax that will break to people. How considerate I am.
alright now sudo make install works
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| sudo make install
make -C module install
make[1]: Entering directory '/home/eduardo/projects/evdi/module'
make -C /lib/modules/5.15.12-200.fc35.x86_64/build M=$PWD INSTALL_MOD_PATH= INSTALL_MOD_DIR=/kernel/drivers/gpu/drm/evdi modules_install
make[2]: Entering directory '/usr/src/kernels/5.15.12-200.fc35.x86_64'
INSTALL /lib/modules/5.15.12-200.fc35.x86_64//kernel/drivers/gpu/drm/evdi/evdi.ko
SIGN /lib/modules/5.15.12-200.fc35.x86_64//kernel/drivers/gpu/drm/evdi/evdi.ko
DEPMOD /lib/modules/5.15.12-200.fc35.x86_64
make[2]: Leaving directory '/usr/src/kernels/5.15.12-200.fc35.x86_64'
true
make[1]: Leaving directory '/home/eduardo/projects/evdi/module'
make -C library install
make[1]: Entering directory '/home/eduardo/projects/evdi/library'
install -d /usr/local/lib
install -m 755 libevdi.so.1.10.0 /usr/local/lib/libevdi.so.1.10.0
ln -sf libevdi.so.1.10.0 /usr/local/lib/libevdi.so.0
ln -sf libevdi.so.0 /usr/local/lib/libevdi.so
make[1]: Leaving directory '/home/eduardo/projects/evdi/library'
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as you can see the module is there:
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| find /lib/modules/(uname -r) -name "*.ko" | grep -i evdi
/lib/modules/5.15.12-200.fc35.x86_64/kernel/drivers/gpu/drm/evdi/evdi.ko
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so it’s just a matter of loading that module with
and done!
conclusion
as you can see the process is pretty manual process, which most of the times is similar. let’s see if i can remember posting the process every time it breaks again.