[Gta04-owner] Upstream Replicant 4.2 support for GTA04

[Paul Kocialkowski]

As I wrote in my previous message, I'm giving the GTA04 a new try at
Replicant 4.2. I see that you have been busy during the time I retired
and I'm glad some progress was made, especially on the kernel.

I just tried Alexandre's Replicant 4.2 images and the suspend/resume
issues seem to have vanished.

However, I encountered some issues related to the kernel:
* OTG seems to work fine but refuses to configure USB flash drivers
since they apparently ask too much current: this doesn't look like
normal behavior.
* The battery driver seems not to work (the sysfs nodes all return
errors). I suspect this is because of the 1-wire interface.
* ADB driver seems to crash at poweroff
* Plugging the USB cable before the device is booted made my host
computer crash several times, with kernel panic
* I'm not sure audio worked all the time after suspend/resume

These are just quick notes, we should look deeper in details for all
these points.

I am going to start over the Replicant 4.2 bringup on my own since I
dislike some of the changes that were made on the goldelico replicant
trees:
* The Replicant logo in the bootanimation is too small, it should have
420px height.
* GTA04 model detection is unacceptable. The kernel should provide a
sysfs node with that info or something like that, but in no case should
the userspace have to parse dmesg.
* I don't want the single partition approach in Replicant.
* The Wi-Fi firmwares should not be in the source code

I see two ways of correctly performing GTA04 version detection by
userspace. On the kernel side, they involve having a sysfs node that
will provide either a number or a string that matches a particular gta04
variant. Then, the modules should access that information and behave
accordingly.

For accessing the information, modules could either read the sysfs node
directly or communicate by a gta04-specific daemon (gta04d or goldelicod
perhaps) that reads the string and returns it to the module upon request
through a unix socket.

The advantage of having a gta04-specific daemon (called at early-init)
is that it also makes it possible to perform all the variant-specific
actions:
* load the correct battery driver
* swap the correct initlogo.rle/bootanimation.zip for each resolution

These actions could also be done by a single script (the way it's
currently done on the goldelico tree), hence without the possibility of
having a socket. However, I would prefer having a daemon cleanly written
in C code.

On the single partition approach: I understand this is how you like to
do things on regular GNU/Linux systems, but this is Android. It is
mandatory to have separate partitions for /system, /data, /cache and
having an initramfs. Android is built around with that assumption and
not following this scheme will draw incompatibilities. For instance,
features such as encrypting the data partition will be unavailable as
well as wiping the data partition will be unavailable.

I also worked on bringing recovery support (which is something everyone
who installed a community Android version on an Android phone knows
about). It's basically a single binary, packed into an initramfs that
will perform actions such as installing a system zip, wiping /data
(factory reset), making a backup of the system, restoring the backup,
etc. Again, that won't work if we don't have separate partition
for /system, /data and /cache.

On top of that, it doesn't seem outrageous to me to require the whole
sdcard for installing Replicant. That's what it takes.

I also prefer to go with my own minimalistic boot.scr that handles
recovery booting and the Android kernel names (boot.img and
recovery.img).

That's all for now, feel free to share any remark/suggestion.

My next steps are building a full system with my code, then publishing
all the source once the state is as good as 4.0 and then I'll work on
particular hardware features.

-- 
Paul Kocialkowski, Replicant developer

Replicant is a fully free Android distribution

Website:        http://www.replicant.us/
Wiki/Tracker:   http://redmine.replicant.us/
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