epkowa doesn't recognize x770 USB scanner

[neilmayhew]

Describe the bug
Since upgrading to 20.03, the epkowa sane backend isn't working.

To Reproduce
Use scanimage -L to check for the presence of the scanner:

$ lsusb
Bus 001 Device 008: ID 04b8:0130 Seiko Epson Corp. GT-X770 [Perfection V500]
$ scanimage -L
$ 

Expected behavior

$ lsusb
Bus 001 Device 008: ID 04b8:0130 Seiko Epson Corp. GT-X770 [Perfection V500]
$ scanimage -L
device `epkowa:interpreter:001:008' is a Epson Perfection V500 flatbed scanner
$ 

Additional context

1. I've used SANE_DEBUG_SANEI_USB=3 to view the list of USB IDs being checked for, and 04b8:0130 isn't included.
2. I can run the scanimage from 19.09 successfully like this:

$ . /nix/var/nix/profiles/system-369-link/etc/set-environment
$ /nix/var/nix/profiles/system-369-link/sw/bin/scanimage -L
device `epkowa:interpreter:001:008' is a Epson Perfection V500 flatbed scanner
$ 

Notify maintainers
@symphorien @dominikh

Metadata

• system: "x86_64-linux"
• host os: Linux 5.4.42, NixOS, 20.03.1964.a808fe4fcde (Markhor)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.4
• channels(root): "nixos-20.03.1964.a808fe4fcde"
• channels($USER): "nixpkgs-20.09pre226664.002d38783ab"
• nixpkgs: $HOME/.nix-defexpr/channels/nixpkgs

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: epkowa
# a list of nixos modules affected by the problem
module:

[symphorien]

I have no idea what could be the cause as there is no significant commit on epkowa from 19.09 to 20.03, neither on the sane module.
I don't have access to hardware to test at the moment, so I can't investigate much more the quick look I gave at the code...

Maybe try bisecting nixos if you have time to spend ?

[symphorien]

I could reproduce and I think it is fixed by e22eb2d

[neilmayhew]

Thank you. That does seem to fix it. I had already noticed the existence of that patch, but didn't realize that 20.03 didn't have it in. When I run scanimage from today's nixos-unstable-small it recognizes my scanner.

Is there any chance of having this backported to 20.03?

[Ekleog]

With #82909, the backport should now be done, so I'm going to close :) Feel free to complain and/or reopen if the issue is still present!

[neilmayhew]

It's been merged into master but not into release/nixos-20.03:

$ git merge-base origin/release-20.03 e22eb2d7b5078f78655e478dcee3a8298821edf3
7c0d3f6f70c7a55e8c988e9d6882820b9d26171d
$ git merge-base origin/master e22eb2d7b5078f78655e478dcee3a8298821edf3
e22eb2d7b5078f78655e478dcee3a8298821edf3

I'm reopening because I think it's important that this gets into 20.03.

[neilmayhew]

Correction: I'd like to reopen it, but I don't have the necessary permission level.

[Ekleog]

Ugh I linked the last wrong PR, sorry! I meant #89506 :)

(As for the permission level… that's weird, I thought everyone had the right to reopen issues. Well, if you want to reopen feel free to ask and I'll do :))

Edit: looks like that's a github limitation isaacs/github#583

[neilmayhew]

Thanks! That's great. It hasn't hit the channels yet, but I tested it with a NixOS built from the current state of release-20.03 and everything's fine.