On Sun, Mar 07, 2021 at 06:58:10AM +0100, Matthias Schwarzott wrote:

Am 05.03.21 um 20:14 schrieb Alan Stern:

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On Fri, Mar 05, 2021 at 05:54:43PM +0100, Matthias Schwarzott wrote:

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One major difference I noticed looking at service answer time statistics:
Windows sends a lot more requests of type "Test Unit Ready".
* Windows: 6385 calls
* linux: 71 calls

It's generally well known that Windows issues lots and lots of redundant
commands to USB storage drives.


Unless the Kindle advertises removable media, there doesn't seem to be
any real point to all those TEST UNIT READY commands.  Unless they are
what prevents the disconnections...

This is kernel log from connecting:
[41709.248006] usb 3-4: new high-speed USB device number 6 using xhci_hcd
[41709.380015] usb 3-4: New USB device found, idVendor=1949, idProduct=0004,
bcdDevice= 1.00
[41709.380019] usb 3-4: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[41709.380021] usb 3-4: Product: Amazon Kindle
[41709.380022] usb 3-4: Manufacturer: Amazon
[41709.380023] usb 3-4: SerialNumber: REMOVED
[41709.493988] usb-storage 3-4:1.0: USB Mass Storage device detected
[41709.494080] scsi host6: usb-storage 3-4:1.0
[41710.510122] scsi 6:0:0:0: Direct-Access     Kindle   Internal Storage
0100 PQ: 0 ANSI: 2
[41710.510245] sd 6:0:0:0: Attached scsi generic sg3 type 0
[41710.513059] sd 6:0:0:0: Power-on or device reset occurred
[41710.526331] sd 6:0:0:0: [sdc] Attached SCSI removable disk
[41712.629152] sd 6:0:0:0: [sdc] 6688768 512-byte logical blocks: (3.42
GB/3.19 GiB)
[41712.846353] sd 6:0:0:0: [sdc] Write cache: enabled, read cache: enabled,
doesn't support DPO or FUA
[41712.846357] sdc: detected capacity change from 0 to 6688768
[41712.849499]  sdc: sdc1

As it prints "Attached SCSI removable disk" the device advertises removable
media.

Yes.

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How can I get further on this topic?

Is runtime power management enabled?  Maybe the Kindle disconnects
whenever the computer tries to suspend it.  This typically happens 2
seconds after the last command was issued, which matches your
observations.  If runtime PM is enabled, you can try disabling it.

I assume this means autosuspend is not used:

# cat /sys/block/sde/device/power/control
on

This means autosuspend isn't used for the sde drive.  But the log 
extract above shows that the Kindle is sdc, not sde.

Alan Stern