[Samsung Galaxy Tab A series ROMs, Kernels, Recover] retiredtab:
FAQ - I spent hundreds of hours building this rom. The least you can do is spend a few minutes reading everything before posting.

Q1) Does the build work on xyz?

A1) I have no idea. I only have the SM-P550.

One user reported that this rom causes a boot loop on the SM-P555. So if you have this tablet and want to try this rom, just be prepared to revert your changes. According to this post by virsys

https://xdaforums.com/galaxy-tab-a/...50-sm-t555-t3779257/post78327523#post78327523

"You have to use a different kernel config for the SM-T555. The versions here are compiled for the SM-T550 variant and will never work on a SM-T555 properly."

With the above, I can only assume that also applies to the P550 and P555.

Q2) Application xyz doesnt' work. Can you fix it?

A2) I only fix what I use. If you use app xyz and it doesn't work, then go back to the last rom that worked for you.

Q3) My tablet hangs or crashes with this rom. This build is slow and buggy. Can you fix it?

A3) Go back to the last working stable rom for you. This is a work in progress and will have bugs and frequent changes.

Q4) Do you plan to update the rom?

A4) Yes as long as I have high speed Internet, I wil try to release the rom monthly to incorporate the security patches.

Q5) Do you plan to add S-pen?

A5) I don't use the S-pen, but if the code is easy to add and you can tell me where and how to add, I can try. You must provide a github repo and example code on how to add it. I will not answer any requests for S-pen support unless you can show code and repos. If it's too complex, I won't do it and since this is all open source, you are welcome to add it yourself, just like how I fixed the inverted X-axis.

Update Jan 14, 2021.

The S-pen code is highly unstable as it changes 40 or more kernel parameters. While the S-pen works, the tablet randomly reboots so I will not release any rom with S-pen. I spent several weeks trying to troubleshoot the problem, but it's too hard to narrow down the problem.

Q6) Will there be a 17.1 release?

A6) Virsys' github has some 17.1 repos so I will try at some point in the future. No promises. I already built a beta SM-T350, the little brother to the T550, and it took a long time to work out all the bugs in 17.1. 16.0 should be more stable than 17.1 at this point in time.

Q7) Can I turn off the on screen navigation keys?

A7) To turn off on screen navigation, go to settings, system, advanced, gestures, system navigation, gesture navigation.

Q8) How did you fix the inverted X-axis.

A8) For those who don't know, some of the T550 ROMs do boot and work on the P550, but without the S-pen. HOWEVER, the X-axis is reversed. You can read here on my initial testing.

https://xdaforums.com/showpost.php?p=79018037&postcount=108

After some research, it wasn't that hard, but finding the right touchscreen driver and learning how the input system worked took a couple of days. Basically, you look at the kernel defconfig file and look for the CONFIG_TOUCHSCREEN setting. That will tell you what driver it's using.

kernel/samsung/msm8916/arch/arm/configs/msm8916_sec_gt510wifi_eur_defconfig

CONFIG_TOUCHSCREEN_ATMEL_MXT1664T=y

Then you look in the kernel/samsung/msm8916/drivers/input/touchscreen directory to find the correct driver.

The screen resolution of the P550 is 1024x768. For some reason, the current code thinks its 1024x1024 below. 1024x4=4096. It's numbered 0 to 4095. So the ABS_MT_POSITION_X is 4095.

$ adb shell
gt510wifi:/ $ getevent -lp /dev/input/event1
add device 1: /dev/input/event1
name: "sec_touchscreen"
events:
KEY (0001): KEY_BACK 00fb 00fd 00fe
BTN_TOOL_FINGER BTN_TOUCH
ABS (0003): ABS_MT_SLOT : value 0, min 0, max 9, fuzz 0, flat 0, resolution 0
ABS_MT_TOUCH_MAJOR : value 0, min 0, max 255, fuzz 0, flat 0, resolution 0
ABS_MT_TOUCH_MINOR : value 0, min 0, max 255, fuzz 0, flat 0, resolution 0
ABS_MT_POSITION_X : value 0, min 0, max 4095, fuzz 0, flat 0, resolution 0
ABS_MT_POSITION_Y : value 0, min 0, max 4095, fuzz 0, flat 0, resolution 0
ABS_MT_TRACKING_ID : value 0, min 0, max 65535, fuzz 0, flat 0, resolution 0
003e : value 0, min 0, max 1, fuzz 0, flat 0, resolution 0
LED (0011): LED_MISC
input props:
INPUT_PROP_DIRECT
gt510wifi:/ $

The code to fix the inverted X-axis is easy. It's one line. Just 4095 minus the current x-axis position. However, if I can fix the code so it recognizes the tablet correctly as 1024x768, then 4095 changes to 3071 (768 x 4 = 3072).

project kernel/samsung/msm8916/
diff --git a/drivers/input/touchscreen/mxt_t/mxtt.c b/drivers/input/touchscreen/mxt_t/mxtt.c
index 2e0a3fa0fa7..39e8eccabc9 100644
--- a/drivers/input/touchscreen/mxt_t/mxtt.c
+++ b/drivers/input/touchscreen/mxt_t/mxtt.c
@@ -671,7 +671,7 @@ static void mxt_report_input_data(struct mxt_data *data)
input_mt_report_slot_state(data->input_dev,
MT_TOOL_FINGER, true);
input_report_abs(data->input_dev, ABS_MT_POSITION_X,
- data->fingers[i].x);
+ 4095-data->fingers[i].x);
input_report_abs(data->input_dev, ABS_MT_POSITION_Y,
data->fingers[i].y);

Update Nov 9, 2020. I found out later that if the wacom s-pen driver can be implemented reliably, the above patch is not required. That is, the wacom s-pen driver maps the x-axis correctly. Currently, I cannot make a reliable build with the 16.0 or 17.1 code without random reboots when the wacom driver is included. Even without the wacom driver, I'm having problems making a reliable 16.0 and 17.1 rom after the Sept 23, 2020 release.

Q9) Can I build this rom? Where are the kernel source files? I have included the roomservice.xml and repo diff as well.

A9) The kernel source files are at

Samsung MSM8916 Devices

Samsung MSM8916 Devices has 68 repositories available. Follow their code on GitHub.

github.com

aala27 - Repositories

aala27 has 7 repositories available. Follow their code on GitHub.

github.com

Q10) What TWRP should I use?

A10) Use 3.5.2_9 from

retiredtab - Browse /SM-P550/TWRP at SourceForge.net

sourceforge.net

Q11) Where can I download this rom?

A11) 2020 16.0 BETA builds are at

https://androidfilehost.com/?w=files&flid=317066

2021 17.1 BETA builds are at

retiredtab - Browse /SM-P550/17.1 at SourceForge.net

sourceforge.net