Motorola Droid 4 - RTC driver

With Debian up & running I had a look at what needs to be done in the mainline kernel. Tony is working on the ADC parts, which are required for the battery/charger work and mentioned he will have a look at USB. He also mentioned, that somebody with spare cycles could take care of CPCAP’s rtc & watchdog. I had a look at Motorola’s vendor kernel and as far as I can see CPCAP does not come with a watchdog (unlike twl4030/twl6040). Read more →

Power Supply for v4.11

I just sent the power-supply pull request to Linus Torvalds. Regarding to power-supply Linux v4.11 will bring 3 new drivers: sbs-charger max14656-charger-detector axp20x-ac-power As well as newly supported hardware in 4 existing drivers: axp20x_usb_power: AXP223 support tps65217: add usb charger support qcom_smbb: support otg regulator at91-reset: add samx7 support Also we could drop one driver, since the platform it is used for is no longer supported by the Linux kernel: Read more →

Motorola Droid 4 - Debian

In the last post I rooted the Droid 4 and installed LineageOS with SafeStrap as bootloader. Today I took care of getting the mainline kernel running and preparing a rootfs. After some communication with Tony I got the kexec stuff running (at the end the problem was my compiler generating binaries not suitable for Android). Instead of getting a compiler toolchain for Android I decided to rewrite the binary into a shellscript, so that no compiler is required. Read more →

Motorola Droid 4 - rooting

Yesterday I received the Motorola Droid 4 from my previous article. It came in a reasonable condition with a few scratches in the case (none in the display) and some of the back cover’s clips being broken. First impression: The phone feels a bit more clumpy than the N950, but much less than the N900. The sliding mechanism feels qualitatively worse than Nokia’s and the same goes for the keyboard quality. Read more →

Motorola Droid 4

Tony Lindgren is currently working on mainline kernel support for the Motrola Droid 4 (Wikipedia, GSMArena, iFixit Teardown). He documented his work to get serial over USB on the following page: http://muru.com/linux/d4. I just got myself a used one via Ebay, since it’s a decent upgrade from the Nokia N9xx phones. It’s also quite cheap (30$ in US, 50€ after import to DE (shipping + customs)). Last but not least there is no newer phone available, which has a proper hardware keyboard. Read more →

Kernel Driver for Nokia Bluetooth Chips

While improving slowly, the mainline kernel’s support for smartphones is quite bad. One of the better supported phones is the Nokia N900. Apart from a few missing features, which could improve the performance of some operations (like crypto acceleration), its currently lacking support for two missing features: Bluetooth Cameras I worked on both tasks during my master’s thesis, but in this post let’s focus on the Bluetooth module. For Bluetooth support the Nokia N900 has broadcom’s bcm2048 chip (which also supports FM radio, but that’s out of scope for this post). Read more →

MCP23017

Our hackerspace’s access-control-system (for unlocking the door) uses a few mcp23017 port expanders for input/output handling of different sensors and actors. When I started working on this, the mcp23s08 driver (which also supports the mcp23017) was not yet enabled in Debian’s arm build. I requested it to be enabled in Debian Bug #845064, which got recently fixed by Ben Hutchings. As a quick hack to solve the problem I took the driver and ripped it out of the kernel, so that I can build it externally. Read more →