Pavel Machek

https://social.kernel.org/users/pavel

Riding horses, hacking computers, phones and smartwatch.

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npub1hquy5jd6kctnkewwu7mdcykkfcdp3ujeq4c4j6dlrg64zjj0jhys76zr0f

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Last Notes

2026-01-20 18:49:53 UTC

I had many phones. Some were good, some were bad, and some were meh. Siemens sl45i looked like good phone, but it was not, partly because they forgot to debug it. Ericsson t68i was nice (70? grams), bluetooth was improvement. Nokia 6230 was very nice phone (99 grams), Nokia 6230i was downgrade, and Ericsson K700i was not a good phone. UI was not great and it would not hold in one piece.
I had HTC Dream (aka T-Mobile G1). Having Linux inside was "cool" but it definitely was not good, and was not a phone. Nokia N900 was better, Linux worked a bit better, but still not a phone. And than it got ... worse? Motorola Droid 4 is better version of N900, but bigger again. Pine Phone, Librem 5, OnePlus 6 ... yes, each one is better computer, but neither is really a good phone.
And then I got Geeksphone Keon (Firefox OS). It runs Linux (kernel 3.4 or something), but rather old one, and is certainly not a good computer, but it started feeling as a phone, again. Reasonably battery life (few days), and it would actually fit into pockets I had available when riding horses. I liked that one. 120grams.
And now I have a new toy (actually few "new" toys, thanks!) that starts to feel like phone. Siemens S4 mini VE (110 grams) is really nice phone. Small enough and can last few days (with LineageOS), and with #postmarketos it seems to be pretty good computer, too. It runs mainline kernel, and most of the stuff mostly works (except cameras). Wow! Once again, I have phone I like (or four).
Samsung was not even too evil when creating the phone, so you can just hold buttons and enter bootloader. Certainly improvement from OnePlus 6, where I will likely never get rid of red errors during boot. There is a bit of evil in the details, that "VE" or "value edition" is important. That is i915i, which is very, very different from "S4 mini" or i915. Mainline support is very limited for i915 -- you will not get touchscreen, for example.
Any help would be welcome. And if you have S4 mini you do not need, I may be able to use it.
#i915 #i915i

2026-01-03 22:47:16 UTC

I have Samsung S4 Mini (i9195) running close to mainline 6.19. Good. It took me more debugging that it should.
I also have patches that allowed me to trace execution from assembly to init/main.c to pagetable setup in C, using pixels on framebuffer and then with hacked console.

2025-12-28 23:56:38 UTC

Self-built lk2nd simply works on S4 mini. Wow. That was easy :-).

2025-11-25 22:52:36 UTC

Libcamera "simple" example usage has three files, 600 lines total. Good news is that it works, bad news is that it stops working almost as soon as I modify it... and not in a way that is easy to debug (segfault, debug trap, backtrace pointing to source line with "}"). I integrated it with SDL, and that was easy, got buffers mapped and translated to format that can be displayed. But when I try to close front camera and open back one, or to change resolution, bad things (tm) happen. Fact that empty build takes 15 seconds also does not help.
My code is at https://gitlab.com/tui/libcamera/-/commit/456a19f64e1b0959cdc9b1b9fa666963772a383c. Press "Snap" button to demonstrate the problem.
If you can help debugging it, or can get it to work, or know better example to start from, please let me know. Would not mind boosts. You may get libcamera based application to take photos / record videos on phones in future if we can get this to work.

2025-11-15 10:43:08 UTC

Front camera on OnePlus 6 now "works" with libmegapixels. Good. More work ahead.

2025-11-03 09:11:06 UTC

I'm experimenting with sensors on #librem5 (but should work on #linuxphones after tweaks). So far I have compass and step counter. github.com:pavelmachek/Espruino.git

2025-07-17 09:43:20 UTC

#phonecamera #linuxphone #librem5
Librem 5 camera/kernel can do three possible resolutions, ~1024x768 @ ~24fps, ~2048x.. @ ~31 fps and ~4096x.. @ ~15fps. Debayering is actually easier and better quality if we downscale at the same time, and that allows best framerate, so we do that (2048x.. resolution).
ARM has problems with cache coherency w.r.t. DMA, and kernel solution is to simply disable cache on DMAbufs for userspace, which means accessing video data is 10x slower than it should be on the CPU. Which means debayering on GPU is attractive, and that's what we do. (gold.frag). GPU can do more image signal processing functions easily, too, so we do some of that.
Unfortunately, we hit the same uncached memory problem at the GPU output. So we use separate thread to copy. All this unfortunately does not fit on one core, so we need two threads, one controlling GPU debayer on frame n+1, while the other one copies video data from frame n. (heart.c). We save resulting RGBA data to ramdisk. This all costs maybe 80% of one core.
From there, Python scripts can pick them up: ucam.py displaying the viewfinder and mpegize.py handling the video encoding via gstreamer. There's basically 0% cpu left, but I can encode ~1024x.. video. Unfortunately that's without audio and with viewfinder at 1fps. Plus, combination of C + Python is great for prototyping, but may not be that great for performance.
Code is here: https://gitlab.com/tui/tui/-/tree/master/icam?ref_type=heads .
At this point I'd like viewfinder functionality merged into the rest of GPU processing. Ideally, I'd like to have a bitmap with GUI elements, combine it with scaled RGBA data, and rendering it to screen. I know SDL and Gtk, SDL looked like better match, but I could not get SDL and GPU debayering to work in single process (template SDL code is here https://gitlab.com/tui/debayer-gpu/-/blob/master/sdl/main.c?ref_type=heads ).
If you can integrate main.c and heart.c, that would be welcome. If you have example code that combines SDL with processing on GPU, that would be nice, too. If you know someone who can do GPU/SDL, boost would not be bad, I guess.
@npub1mkm…c0eu
@npub1f27…g56p
@npub1ws3…halv
@npub1r3z…03cf

2025-07-01 19:04:44 UTC

edit: Thanks for all the heroes that chimed in. In meantime, I got help from entity that shall not be named, and currently have something fast enough. And I have great human experts on line, with patches to test. Thanks again! :-)
Can you program GPUs and do you want to become a HERO? #linuxphone
community needs your help.
We are trying record video, and have most pieces working, but one is
missing: fast enough debayering. That means about 23MB/sec on #librem5.
Debayering is not hard; camera images have subpixels split on two
lines, which need to be corrected. They also use different color
representation, but that's fixable by some table lookup and two matrix
multiplies.
Librem 5 has Vivante GPU, 4 in-order CPU cores and 3GB RAM. My feeling
is that it should be fast enough for that. If task is for some reason
impossible, that would be good to know, too.
Image data looks like this
RGRGRG...
xBxBxB...
.........
.........
Task is to turn that into usual rgbrgb.... format. rgb = RGB * color
matrix, with table lookups for better quality. I can fix that once I
get an example.
I'm looking for example code (#pinephone would work, too), reasons it
can not be done... and boosts if you have friends that can program
GPUs. #gpu #opensource

2025-05-22 09:11:21 UTC

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Dunno. Perhaps simply avoid running screen-capturing malware? If Microsoft will not allow uninstall of Recall, you can still uninstall Windows...

2025-04-11 20:49:41 UTC

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LLMs have some good uses. "Translate this to czech". "Translate this to Javascript". Other stuff is more hit and miss, but I was able to do "I need graphics format which is basically width/height/fourcc"... and I got that. [And if you know format other than .dds that meets the requirements, let me know.]

2025-04-04 07:53:09 UTC

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Why is "retaliate" bad option? Seems like prisoner's dilemma to me, and retaliation is crucial there.

2025-03-07 07:33:37 UTC

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ToS only applies to Firefox binaries. Get sources, or get your binaries from Debian who gets sources.

2025-02-08 20:25:27 UTC

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Is that those "power button with fingerprint sensor" thingies? I guess we'll first want the fingerprint stuff working, but yes, that could be useful.

2025-02-08 20:21:25 UTC

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Yeah, except that's focus, not optical zoom. But I guess we'll need something on touchscreen. I suggest taking focus/exposure on press, and taking photo on release.

2025-02-07 12:23:28 UTC

So everyone is taking pictures with #oneplus6 #mobilelinux #postmarketos . Can you get me some metadata? Which sensor works, resolution, what format does it use? (BGGR8? BGGR10? Something better?) I am using Librem 5, but that only has 8-bit bayer working (and many other problems).

2024-12-03 20:52:01 UTC

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If you consider zerophone viable, you should consider oneplus 6, too. All are usable. PinePhone and Librem 5 are a bit slow for today's web.

2024-12-01 17:20:11 UTC

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How well does Linux work with s2idle? All stable/reliable/works on all hw that supports it?

2024-10-23 07:13:05 UTC

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Dells have them, too. I'm pretty sure those patents are already expired.

2024-10-17 10:20:14 UTC

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1) Still does not mean that people should not randomize IMEIs. If randomized IMEIs will become common, world will improve. In 1995 Linux was uncommon and would "draw attention". Today, it is very good idea. 3) agreed. IMO we should still try to improve cellular privacy.

2024-09-15 09:48:09 UTC

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Of course, Furilabs can do the minimum required by law, but what was the reason to care about their hardware? Fairphone is actually doing more than minimum required -- they are working on upstreaming their kernel changes, perhaps take that one, instead? Or PinePhone? Or Librem 5? Ore OnePlus 6 (where vendor did the minimum but community is doing lot more)?

2024-09-03 13:03:18 UTC

Moving closer to usable cameras. https://gitlab.com/megapixels-org/Megapixels/-/merge_requests/29