[Nook Touch General] CrisCraigMorgan:
Hm, well my mdns library conflict turned out to be a red herring; "adb push" is failing while actually trying to send the data over the USB line:

76447 libusb CALL read(0x8,0x7fffdf9faecf,0x1)
76447 libusb RET read -1 errno 35 Resource temporarily unavailable
76447 libusb CALL ioctl(0xd,USB_FS_COMPLETE,0x7fffdf9fae38)
76447 libusb RET ioctl 0
76447 libusb CALL ioctl(0xd,USB_FS_COMPLETE,0x7fffdf9fae38)
76447 libusb RET ioctl -1 errno 16 Device busy
76447 libusb CALL ioctl(0xd,USB_FS_START,0x7fffdf9fad40)
76447 libusb RET ioctl 0
76447 libusb CALL poll(0x7fffdf9fae90,0x2,0xffffffff)
76447 libusb RET poll 1
76447 libusb CALL read(0x8,0x7fffdf9faecf,0x1)
76447 libusb RET read -1 errno 35 Resource temporarily unavailable
76447 libusb CALL ioctl(0xd,USB_FS_COMPLETE,0x7fffdf9fae38)
76447 libusb RET ioctl 0
76447 libusb CALL ioctl(0xd,USB_FS_COMPLETE,0x7fffdf9fae38)
76447 libusb RET ioctl -1 errno 16 Device busy
76447 libusb CALL _umtx_op(0x800b7a6b8,UMTX_OP_NWAKE_PRIVATE,0x1,0,0)
76447 libusb RET _umtx_op 0
76447 libusb CALL poll(0x7fffdf9fae90,0x2,0xffffffff)
76447 adb RET _umtx_op 0
76447 adb CALL getpid
76447 adb RET getpid 76447/0x12a9f
76447 adb CALL write(0x2,0x7fffdf1f65a0,0x67)
76447 adb GIO fd 2 wrote 103 bytes
"adb E 07-28 21:47:41 76447 102116 transport_usb.cpp:167] remote usb: 2\
- write terminated: No error: 0
"

Currently, I can't push data with adb except via adb shell, which is not optimal.

Also, the MTP issue isn't quite what I first thought. I tried using various MTP and PTP clients (setting the USB mode on the Nook to MTP/PTP respectively), and almost all of them failed to work. Some just hung; some intermittently showed the directory structure that was expected to be exported over MTP but did not allow to create any files/directories. One, jmtpfs, actually seemed to work -- sort of. With this MTP implementation, I can reliably see a couple of directories, only one of which is writable. But I can reliably write files into that directory, so at least I have a way to copy data from the computer to the Nook.

This is what the host sees when I mount the device with jmtpfs:

frappe/mnt/android-14502# ps ax |grep -i mt
69792 - Is 0:00.01 jmtpfs /mnt/android

frappe/mnt/android-14503# mount | grep fuse
/dev/fuse on /mnt/android (fusefs)

frappe/mnt/android-14508# find .
.
./SD card
./Internal storage
./Internal storage/Digital Editions

Only that "Digital Editions" directory is writable. On the Nook side, it looks like this:

root@ntx_6sl:/data/media/0 # ls -l
drwxrwxr-x media_rw media_rw 2020-07-29 01:28 Android
drwxrwxr-x media_rw media_rw 2020-07-28 23:07 DCIM
drwxrwxr-x media_rw media_rw 2020-07-29 01:27 Digital Editions
drwxrwxr-x media_rw media_rw 2012-09-19 19:57 Documents
drwxrwxr-x media_rw media_rw 2020-07-27 18:35 NOOK
drwxrwxr-x media_rw media_rw 2020-07-28 23:07 Pictures

That directory structure is also mounted again, locally on the Nook, as some kind of fuse filesystem:

root@ntx_6sl:/mnt/shell/emulated/0 # ls -l
drwxrwx--x root sdcard_r 2020-07-29 01:28 Android
drwxrwx--- root sdcard_r 2020-07-28 23:07 DCIM
drwxrwx--- root sdcard_r 2020-07-29 01:27 Digital Editions
drwxrwx--- root sdcard_r 2012-09-19 19:57 Documents
drwxrwx--- root sdcard_r 2020-07-27 18:35 NOOK
drwxrwx--- root sdcard_r 2020-07-28 23:07 Pictures

Exploring the files in /init*rc, I see some amount of symlinking, setting USB VID/PID combos, etc, based on the usb config setting, but I don't see anything that would specifically share or not share those subdirectories, nor map the mountpoint "SD Card" and "Internal Storage". Any pointers here appreciated.

---------- Post added at 10:45 AM ---------- Previous post was at 10:40 AM ----------

For anyone else trying to get this device working, I also discovered that the warm-light function of the front-light can be controlled by writing into "/sys/class/backlight/lm3630a_led/color". Writing a numeric ASCII value between 0 and 10 into this file changes the degree of warmth on the display: 0 is the most red, and 10 (the default) is the most white. I don't see any way of controlling this from the control panel, nor from the e-reader apps I've tried.