[PATCH v2 0/2] SANE: fix a locking bug for plustek backend

Hi.

While attempting to use a Canon LiDE 30 scanner, which is supported by SANE in

its current version, I noticed a malfunction with the plustek backend. No

application seemed capable of detecting the scanner, even though the

`sane-find-scanner` command indicated its presence, and the device IDs matched

those in the plustek backend configuration.

I investigated further using the following command:

SANE_DEBUG_SANEI_USB=128 SANE_DEBUG_PLUSTEK=255 strace -fye open,openat scanimage -L

Here is a summary of the output:

[23:00:21.688008] [plustek] usbDev_open(auto,) - 0x1c1e5630

[pid 1209-20241] openat(AT_FDCWD</home/neox>, "/gnu/store/gzc1m4n79d1fgby8l58dsaq7nrzyhc14-sane-backends-1.3.1/var/lock/LCK..libusb:001:009", O_WRONLY|O_CREAT|O_EXCL, 0644) = -1 EROFS (Read-only file system)

[23:00:21.688089] [plustek] sanei_access_lock failed: 11

[23:00:21.688131] [plustek] open failed: -1

It seems that the issue is the attempt to open a lock file in the store, which

is not possible due to the read-only nature of the file system.

To address this, there were two possible approaches: either move the lock file

to another location or disable the locking mechanism altogether.

After some research, I found that this bug has been resolved in both Debian [1]

and nixOS [2], and it has also been reported to the upstream project [3]. Debian

opted to disable the locking mechanism, while nixOS moved the lock file to a

runtime-generated location using systemd (by patching the install phase to

prevent the creation of the lock directory). However, since the locking

mechanism allows the use of multiple devices simultaneously[4], which can be

useful, nixOS's solution appears to be the better approach. I followed this

method, proposing to create the lock directory during the activation of the

sane service.

I tested these patch with my Canon LiDE 30 and have been able to (finally)

scan with it.

[1] Debian bug report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=973490

[2] nixOS bug report: https://github.com/NixOS/nixpkgs/issues/273280

[3] Upstream issue: https://gitlab.com/sane-project/backends/-/issues/363

[4] https://gitlab.com/sane-project/backends/-/issues/363#note_443142177

Adrien 'neox' Bourmault (2):

gnu: sane-backends-minimal: fix lock path for plustek backend

services: sane-service-type: create lock path for plustek backend

gnu/packages/scanner.scm | 9 ++++++++-

gnu/services/desktop.scm | 13 +++++++++++++

2 files changed, 21 insertions(+), 1 deletion(-)

base-commit: 1b6ce1796abdf497f61f426d61339318f4f4f23d

--

2.46.0

[arguments]<#:configure-flags>: add "--with-lockdir=/var/lock/sane"

[arguments]<#:phases>: add disable-lockdir-creation to prevent creating the

lockpath during install

Change-Id: I338c16cd4c0bfa0d165c9906b0f1f87ab79a4f75

---

gnu/packages/scanner.scm | 9 ++++++++-

1 file changed, 8 insertions(+), 1 deletion(-)

service to create the lockpath and give the right permissions

Change-Id: I187886d12b5f0b4fe21b03de178ea2187205387a

---

gnu/services/desktop.scm | 13 +++++++++++++

1 file changed, 13 insertions(+)

user guix

merge 73391 73392 73393

quit

Hi, I just realized I forgot to add my copyright notice in the files I

modified. This v2 fixes this.

Adrien 'neox' Bourmault (2):

gnu: sane-backends-minimal: fix lock path for plustek backend

services: sane-service-type: create lock path for plustek backend

gnu/packages/scanner.scm | 10 +++++++++-

gnu/services/desktop.scm | 14 ++++++++++++++

2 files changed, 23 insertions(+), 1 deletion(-)

base-commit: 1b6ce1796abdf497f61f426d61339318f4f4f23d

--

2.46.0

[arguments]<#:configure-flags>: add "--with-lockdir=/var/lock/sane"

[arguments]<#:phases>: add disable-lockdir-creation to prevent creating the

lockpath during install

Change-Id: I338c16cd4c0bfa0d165c9906b0f1f87ab79a4f75

---

gnu/packages/scanner.scm | 10 +++++++++-

1 file changed, 9 insertions(+), 1 deletion(-)

service to create the lockpath and give the right permissions

Change-Id: I187886d12b5f0b4fe21b03de178ea2187205387a

---

gnu/services/desktop.scm | 14 ++++++++++++++

1 file changed, 14 insertions(+)

user guix

merge 73393 73406

quit

user guix

unmerge 73406

unmerge 73393

merge 73391 73392 73393 73406

quit

user guix

unmerge 73406

thanks

user guix

unmerge 73393

thanks

user guix

merge 73391 73392 73393 73406

quit

user guix

retitle 73393 [PATCH v2 0/2] SANE: fix a locking bug for plustek backend

quit