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crocket Guru
Joined: 29 Apr 2017 Posts: 558
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Posted: Sat Mar 02, 2019 11:36 pm Post subject: The horror story of linux kernel |
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Let me explain the horror story. (The short version // Linux kernel let dependencies slip through cracks. It took days for a mere user like me to debug the issue.)
DRM_RADEON should depend on DRM_FBDEV_EMULATION and I2C_CHARDEV, but it doesn't.
Without DRM_FBDEV_EMULATION, DRM_RADEON loses video signal on all virtual consoles and garbles an X session for the first few seconds.
Without I2C_CHARDEV, DRM_RADEON becomes white on all virtual consoles.
DRM_RADEON should not initialize before I2C_CHARDEV. Because DRM_RADEON is oblivious of I2C_CHARDEV, DRM_RADEON may or may not initialize before I2C_CHARDEV.
If I2C_CHARDEV=y and DRM_RADEON=m, DRM_RADEON never initializes before I2C_CHARDEV does. If I2C_CHARDEV=y and DRM_RADEON=y, DRM_RADEON may or may not initialize before I2C_CHARDEV does.
It took days of trial and error to pinpoint the cause of DRM_RADEON's issue. At first, I just guessed relevant kernel config options, but it was too inefficient. Eventually, I started comparing differences between kernel configs that work and those that don't.
Based on differences, my trials became more accurate. Eventually, I narrowed the issue down to DRM_FBDEV_EMULATION and I2C_CHARDEV.
What a horror story. I assumed linux kernel wouldn't let dependencies slip through cracks.
Last edited by crocket on Sun Mar 03, 2019 1:12 am; edited 1 time in total |
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NeddySeagoon Administrator
Joined: 05 Jul 2003 Posts: 54809 Location: 56N 3W
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Posted: Sun Mar 03, 2019 12:17 am Post subject: |
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crocket,
Rule 1. Assume nothing.
I spent most of a day on IRC helping fix sound. Lots of kernel rebuilds later, it was established that the kernel was correct a long time age. It just wasn't being installed.
I assumed ... _________________ Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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bammbamm808 Guru
Joined: 08 Dec 2002 Posts: 548 Location: Hawaii
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Posted: Sun Mar 03, 2019 8:26 pm Post subject: Re: The horror story of linux kernel |
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crocket wrote: | It took days of trial and error |
Welcome to the world of FOSS. _________________ MSI MAG B550 Tomahawk
Ryzen 3900x
32Gb Samsung B-die (16GB dual rank x2) DDR4 @ 3200MHz, cl14
Geforce RTX 2070S 8GB
Samsung m.2 NVME pcie-3.0
Etc.... |
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freke Veteran
Joined: 23 Jan 2003 Posts: 1050 Location: Somewhere in Denmark
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Posted: Sun Mar 03, 2019 8:54 pm Post subject: |
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NeddySeagoon wrote: | crocket,
Rule 1. Assume nothing.
I spent most of a day on IRC helping fix sound. Lots of kernel rebuilds later, it was established that the kernel was correct a long time age. It just wasn't being installed.
I assumed ... |
The quote really is: https://www.youtube.com/watch?v=7rr88Szc5q0 |
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proteusx Guru
Joined: 21 Jan 2008 Posts: 340
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Posted: Mon Mar 04, 2019 1:19 am Post subject: |
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So, for now, what are the best settings for I2C_CHARDEV, DRM_FBDEV_EMULATION and DRM_RADEON? |
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crocket Guru
Joined: 29 Apr 2017 Posts: 558
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Posted: Mon Mar 04, 2019 3:12 am Post subject: |
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proteusx wrote: | So, for now, what are the best settings for I2C_CHARDEV, DRM_FBDEV_EMULATION and DRM_RADEON? |
I2C_CHARDEV=y
DRM_FBDEV_EMULATION=y
DRM_RADEON=m |
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