This page aims to document which existing ebook readers could become RYF certified without too much work.
This is to see what the pros and the cons of liberating an existing e-reader versus making one.
RYF interpretation and resulting hardware choices
Some e-readers contains hardware components that doesn't work with free software (like WiFi chips requiring a nonfree firmware). To prevent such components from getting into the way of the RYF compliance, such components can be disabled in hardware.
If a hardware block is present but typically not used (for instance if a device has a GPU but doesn't use it because it uses an e-ink display which has a high latency), it *may* not get into the way of RYF compliance, as it *probably* won't steers users towards nonfree software.
Questions
For the I.MX GPU (vivante):
Is it required to have a free software driver for GPU when the device is meant to be used as an e-reader and has a high latency e-ink display?
If so, is the free software driver for the vivante GPU sufficently mature not to steer users towards non-free software ?
Existing hardware
Hardware Requirements
Basic requirements
Free boot software or the ability to easily port one to the e-reader.
Enough RAM to run free software operating systems.
No cellphone network support
Good SOC and no crucial peripherals requiring nonfree firmware (else the peripheral will be disabled in hardware)
e-paper display
Requirements to do hardware support work faster
Since e-readers without WiFi or telephony network connection are old, the software they come with and the corresponding source code is also really old.
To be able to use modern GNU/Linux or Android distribution on them, the source code needs to be used to add support for the device in recent hardware support software such as Linux or free software boot software like u-boot.
Software support that helps:
Most of the hardware of the device already supported by upstream projects (Linux and a free software bootloader).
Hardware features that helps:
Serial port that is easy to access
Booting the Bootloader from the USB or serial port
Ethernet (unlikely to be found on such devices)
Requirements that can be lifted
Requirement
Rationale
The absence of WiFi/Bluetooth
The chips could be disabled by soldering some of their pins or by removing them with a hot air gun.
unsigned bootloaders
This requirements can be lifted on devices with the following System On a Chip, if they were made before July 2017:
NXP I.MX6 Quad
NXP I.MX6 QuadPlus
NXP I.MX6 Dual
NXP I.MX6 DualLite
NXP I.MX6 DualPlus
NXP I.MX6 Solo
NXP I.MX6 SoloX
NXP I.MX6 SoloLite
NXP I.MX6 UltraLite
NXP I.MX6 ULL
NXP I.MX53
NXP I.MX50
NXP VFxxx
This is because such chip contains a hardware security flaw enabling to execute your code nevertheless.
Additional requirements
Requirement
Rationale
Recent
Easily available new and second hand.
Battery being new or still in good conditions
More RAM is better
Devices with not enough RAM may not be able to use modern FSDG distributions. Creating a specific distribution for such devices would require someone to maintain it.
Touchscreen
This enables to use most of the Android applications and alleviate the need for custom software that works with buttons only.
Stylus
This enables to use most of the GNU/Linux applications and alleviate the need for custom software that works with buttons or capacitive touchscreens only.
ARMv7 CPUs (x86 is probably not used on e-readers)
CPU that is supported by FSDG distributions or the ability to support the CPU with very few maintenance cost.
* CYTTSP5 Touchscreen
* TPS65185 PMIC
* EPDC
* RC5T619 PMIC:
* RTC (arrived in 5.7-rc1)
* ADC (arrived in 5.7-rc1)
* fuel gauge (battery voltage can be read though ADC)
* charger (gives some 350mA standard charge without driver)
Netronix E60K02
Kobo
Tolino Shine 3
NXP i.MX6 SoloLite
512M
e-ink
Yes
serial port pins marked
internal uSD socket
partial devicetree in 5.6, missing drivers:
* CYTTSP5 Touchscreen
* TPS65185 PMIC
* EPDC
* RC5T619 PMIC:
* RTC (since 5.7-rc1)
* ADC (since 5.7-rc1)
* fuel gauge (battery voltage can be read though ADC)
* charger (gives some 350mA standard charge without driver)
This section has more details on the various chips and other components used in existing e-readers, or that could be used (or should not be used) to build an RYF compliant e-reader.
Considerations
Components
e-ink displays
e-ink displays have a huge latency. I'm not sure if special software is needed to handle it or if Linux standard e-ink drivers are enough.
Available software:
F-droid has a laucnher for e-ink displays
I.MX6 e-ink display controller
In the imx_3.9.11_1.0.0_ga branch in the linux-imx, in video/fbdev/mxc, both mxc_epdc_fb.c and mxc_epdc_v2_fb.c uses request_firmware functions, but they seem to be used to load some wavform (data to drive the display) into the display or display controller.
https://elinux.org/RaspberryPi_Laptop : "Alternative components: E-ink [...] have been hacked to display video with a relatively fast refresh rate" => May contain information about waveforms
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