linux-kernel - Re: [PATCH v2] HID: ft260: fix device removal due to USB disconnect

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Message-ID: <nycvar.YFH.7.76.2107291238490.8253@cbobk.fhfr.pm>
Date:   Thu, 29 Jul 2021 12:39:03 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Michael Zaidman <michael.zaidman@...il.com>
cc:     benjamin.tissoires@...hat.com, aaron.jones@...ichip.com,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH v2] HID: ft260: fix device removal due to USB
 disconnect

On Thu, 29 Jul 2021, Michael Zaidman wrote:

> This commit fixes a functional regression introduced by the commit 82f09a637dd3
> ("HID: ft260: improve error handling of ft260_hid_feature_report_get()")
> when upon USB disconnect, the FTDI FT260 i2c device is still available within
> the /dev folder.
> 
> In my company's product, where the host USB to FT260 USB connection is
> hard-wired in the PCB, the issue is not reproducible. To reproduce it, I used
> the VirtualBox Ubuntu 20.04 VM and the UMFT260EV1A development module for the
> FTDI FT260 chip:
> 
> Plug the UMFT260EV1A module into a USB port and attach it to VM.
> 
> The VM shows 2 i2c devices under the /dev:
>     michael@...hael-VirtualBox:~$ ls /dev/i2c-*
>     /dev/i2c-0  /dev/i2c-1
> 
> The i2c-0 is not related to the FTDI FT260:
>     michael@...hael-VirtualBox:~$ cat /sys/bus/i2c/devices/i2c-0/name
>     SMBus PIIX4 adapter at 4100
> 
> The i2c-1 is created by hid-ft260.ko:
>     michael@...hael-VirtualBox:~$ cat /sys/bus/i2c/devices/i2c-1/name
>     FT260 usb-i2c bridge on hidraw1
> 
> Now, detach the FTDI FT260 USB device from VM. We expect the /dev/i2c-1
> to disappear, but it's still here:
>     michael@...hael-VirtualBox:~$ ls /dev/i2c-*
>     /dev/i2c-0  /dev/i2c-1
> 
> And the kernel log shows:
>     [  +0.001202] usb 2-2: USB disconnect, device number 3
>     [  +0.000109] ft260 0003:0403:6030.0002: failed to retrieve system status
>     [  +0.000316] ft260 0003:0403:6030.0003: failed to retrieve system status
> 
> It happens because the commit 82f09a637dd3 changed the ft260_get_system_config()
> return logic. This caused the ft260_is_interface_enabled() to exit with error
> upon the FT260 device USB disconnect, which in turn, aborted the ft260_remove()
> before deleting the FT260 i2c device and cleaning its sysfs stuff.
> 
> This commit restores the FT260 USB removal functionality and improves the
> ft260_is_interface_enabled() code to handle correctly all chip modes defined
> by the device interface configuration pins DCNF0 and DCNF1.
> 
> Signed-off-by: Michael Zaidman <michael.zaidman@...il.com>
> Acked-by: Aaron Jones (FTDI-UK) <aaron.jones@...ichip.com>

Thanks for the respin. Queued in for-5.14/upstream-fixes.

-- 
Jiri Kosina
SUSE Labs