i/builtin: add gpio-chardev interface #15172

ZeyadYasser · 2025-03-05T18:04:17Z

This implements the gpio-chardev interface according to the SD129 spec which is currently hidden behind an experimental feature flag until kernel improvements to the gpio-aggreagtor lands.

Also, I had to extend the systemd backend to support specifying Wants/WantedBy/After/Before directives 44562bb.

codecov · 2025-03-05T18:24:14Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (d6d95f0) to head (96e9663).
Report is 47 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #15172       +/-   ##
===========================================
- Coverage   78.09%        0   -78.10%     
===========================================
  Files        1190        0     -1190     
  Lines      158458        0   -158458     
===========================================
- Hits       123746        0   -123746     
+ Misses      27017        0    -27017     
+ Partials     7695        0     -7695

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github-actions · 2025-03-05T19:57:26Z

Wed Mar 26 18:47:33 UTC 2025
The following results are from: https://github.com/canonical/snapd/actions/runs/14079689269

Failures:

Preparing:

openstack:debian-sid-64
openstack:debian-sid-64
openstack:debian-sid-64
openstack:debian-sid-64
openstack:debian-sid-64
openstack:debian-sid-64
openstack:opensuse-15.6-64
openstack:opensuse-15.6-64
openstack:opensuse-15.6-64
google:ubuntu-25.04-64:tests/main/snap-ns-forward-compat

Executing:

openstack:debian-12-64:tests/main/progress
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-pre-download:close
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh:parallel
openstack:opensuse-tumbleweed-64:tests/main/snap-refresh-hold
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-backoff
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-pre-download:restart
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-pre-download:ignore
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-gating-from-snap
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-pre-download:close_mid_restart
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh:regular
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-gating
openstack:opensuse-tumbleweed-64:tests/main/auto-refresh-retry
openstack:opensuse-tumbleweed-64:tests/main/refresh-app-awareness-notify
google:ubuntu-25.04-64:tests/main/microk8s-smoke:edge
google:ubuntu-22.04-64:tests/main/prepare-image-classic
google:ubuntu-18.04-64:tests/main/preseed-lxd

Restoring:

openstack:opensuse-15.6-64
openstack:opensuse-15.6-64
openstack:opensuse-15.6-64
openstack:opensuse-tumbleweed-64:tests/main/refresh-app-awareness-notify

bboozzoo · 2025-03-06T12:02:16Z

interfaces/builtin/gpio_chardev.go

+	return lines, nil
+}
+
+func validateLines(linesAttr string) error {


this could be made a helper in strutil, e.g.:

// RangeSpan represents a span of numbers inside a range. A span with // equal Start and Stop describes a span of a single number. type RangeSpan struct { Start, Stop uint } // Range of discrete numbers represented as set of non overlapping spans. type Range struct { // Spans within the range, ordered by Start. Spans []RangeSpan } // ParseRange parses a range represented as a string. The entries are // joining them with a comma: n[,m] or as a range: n-m or a combination // of both, assuming the ranges do not overlap, e.g.: n,m,x-y. func ParseRange(in str, expectedMax uint) (Range, error) { ... }

and then you can reuse it in the helper. Separately I'd add something to the gadget package, or a subpackage there to convert range to a sequence of lines, which should be quite trivial at this point.

Thanks, this now could easily be shared with the helper command, about converting a range into a sequence of lines, I don't think we really need this as the kernel in fact accepts this exact format.

interfaces/builtin/gpio_chardev.go

strutil/range.go

strutil/range_test.go

pedronis

this looks reasonable to me

pedronis · 2025-03-11T17:28:31Z

strutil/range.go

+}
+
+func parseRangeSpan(in string) (RangeSpan, error) {
+	hasNegativeStart := strings.HasPrefix(in, "-")


do we need the negative range support?

not at all, I discussed dropping it with @ZeyadYasser

Switched to using uints

interfaces/builtin/gpio_chardev.go

strutil/range.go

strutil/range_test.go

interfaces/builtin/gpio_chardev.go

interfaces/builtin/gpio_chardev_test.go

bboozzoo

LGTM

pedronis

thanks, couple of small things, question for @bboozzoo

pedronis · 2025-03-12T13:56:22Z

strutil/range.go

+// ParseRange parses a range represented as a string. The entries are joining
+// them with a comma: n[,m] or as a range: n-m or a combination of both, assuming
+// the ranges are non-negative and do not overlap, e.g.: n,m,x-y.
+func ParseRange(in string) (Range, error) {


nitpick: s/in/input/ or s/in/s/

pedronis · 2025-03-12T13:57:01Z

strutil/range.go

+	// Parse range e.g. 2-5
+	tokens := strings.SplitN(in, "-", 2)
+	if len(tokens) != 2 {
+		return RangeSpan{}, fmt.Errorf("invalid range span %q", in)


this error is not tested

This check is not reachable since input that doesn't contain - will have already been parsed as a single number, and doing SplitN on a string that has - will always have exactly two tokens.

The check is redundant, but good to have in case SplitN was swapped to Split for any reason or by mistake.

pedronis · 2025-03-12T14:00:43Z

interfaces/builtin/gpio_chardev.go

+	return nil
+}
+
+// XXX: What should be the limit on max range.


@bboozzoo any suggestion here? is there a limit in the kernel? otherwise we should just remove the XXX

we can set it to 512, which would still be very high and unlikely to ever be reached in practice.

ZeyadYasser · 2025-03-13T12:47:38Z

I had to rebase to resolve conflicts

pedronis

thanks

strutil/range.go

zyga

Thanks for the improvements. I did a longer pass.

I have some small fixes/improvements to the range code and some questions and comments to the interface code. Please see inline.

strutil/range.go

zyga · 2025-03-19T13:29:59Z

strutil/range.go

+	"strings"
+)
+
+// RangeSpan represents a span of numbers inside a range. A span with


Nitpick. I tried to make sense of the naming of RangeSpan and Range but I keep feeling those are off. Could this be just Span and the other one Spans? Feel free to ignore.

I don't have strong opinions on this, @bboozzoo @pedronis what do you think?

strutil/range.go

interfaces/builtin/gpio_chardev.go

interfaces/systemd/service.go

zyga · 2025-03-24T08:54:46Z

interfaces/builtin/gpio_chardev.go

+	"github.com/snapcore/snapd/strutil"
+)
+
+// TODO: Snapd should validate the correctness of slot declarations


What's the plan to implement this after this PR lands?

Yes, It is tracked as https://warthogs.atlassian.net/browse/SNAPDENG-31777

zyga

Mostly LGTM, my main remaining question is the TODO up top in gpio_chardev.go. I have some concerns about reexec on old snapd. Deferring my vote until those two are answered.

zyga

LGTM

jslarraz

LGTM

ZeyadYasser · 2025-03-24T21:55:03Z

For awareness, I found a stupid bug where the slot name was used as the plug name for the symlink generation, I fixed it in b80228a and updated the unit tests to catch it.

Signed-off-by: Zeyad Gouda <[email protected]>

This implements the gpio-chardev interface (spec SD129) which is currently hidden behind an experimental feature flag until kernel improvements to the gpio-aggreagtor lands. Signed-off-by: Zeyad Gouda <[email protected]>

Signed-off-by: Zeyad Gouda <[email protected]>

- strutil: fix range helper typo s/Intersets/Intersects - strutil: only support positive numbers in ParseRange - strutil: sort range spans in ParseRange - i/builtin/gpio-chardev: error message improvements - i/builtin/gpio-chardev: remove unnesaccery non-negative validation Signed-off-by: Zeyad Gouda <[email protected]>

Signed-off-by: Zeyad Gouda <[email protected]>

* i/systemd: support Wants/WantedBy/After/Before directives Signed-off-by: Zeyad Gouda <[email protected]> * i/builtin: add gpio-chardev interface This implements the gpio-chardev interface (spec SD129) which is currently hidden behind an experimental feature flag until kernel improvements to the gpio-aggreagtor lands. Signed-off-by: Zeyad Gouda <[email protected]> * strutil: add range parsing helper Signed-off-by: Zeyad Gouda <[email protected]> * fixup! i/builtin: use strutil.ParseRange helper Signed-off-by: Zeyad Gouda <[email protected]> * fixup! i/builtin: add source-chip validation Signed-off-by: Zeyad Gouda <[email protected]> * fixup! many: address review comments - strutil: fix range helper typo s/Intersets/Intersects - strutil: only support positive numbers in ParseRange - strutil: sort range spans in ParseRange - i/builtin/gpio-chardev: error message improvements - i/builtin/gpio-chardev: remove unnesaccery non-negative validation Signed-off-by: Zeyad Gouda <[email protected]> * fixup! strutil: typo fix and test coverage improvement Signed-off-by: Zeyad Gouda <[email protected]> * fixup! i/builtin: use dirs.DistroLibExecDir instead of fixed path Signed-off-by: Zeyad Gouda <[email protected]> * fixup! i/builtin: fix release info mocking order Signed-off-by: Zeyad Gouda <[email protected]> * tests: exclude gpio-chardev interface from document-interfaces-url Signed-off-by: Zeyad Gouda <[email protected]> * fixup! address review comments Signed-off-by: Zeyad Gouda <[email protected]> * fixup! strutil: simplify Range into a slice of RangeSpan Signed-off-by: Zeyad Gouda <[email protected]> * fixup! many: address review comments Signed-off-by: Zeyad Gouda <[email protected]> * fixup! i/builtin: fix typo of plug name using slot name Signed-off-by: Zeyad Gouda <[email protected]> --------- Signed-off-by: Zeyad Gouda <[email protected]>

ZeyadYasser added the Needs Samuele review Needs a review from Samuele before it can land label Mar 5, 2025

ZeyadYasser requested review from bboozzoo and pedronis March 5, 2025 18:04

bboozzoo reviewed Mar 6, 2025

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ZeyadYasser requested a review from bboozzoo March 7, 2025 10:22

ZeyadYasser added the Needs security review Can only be merged once security gave a :+1: label Mar 10, 2025

bboozzoo reviewed Mar 11, 2025

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ZeyadYasser requested review from bboozzoo and pedronis March 12, 2025 08:28

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ZeyadYasser force-pushed the gpiod-chardev-interface branch from 71b8a46 to 7c6db0b Compare March 13, 2025 12:47

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pedronis approved these changes Mar 13, 2025

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ZeyadYasser mentioned this pull request Mar 15, 2025

cmd/snap-gpio-helper: add gpio-chardev export/unexport commands #15212

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ZeyadYasser added 14 commits March 26, 2025 11:14

i/systemd: support Wants/WantedBy/After/Before directives

02b01c3

Signed-off-by: Zeyad Gouda <[email protected]>

i/builtin: add gpio-chardev interface

0645915

This implements the gpio-chardev interface (spec SD129) which is currently hidden behind an experimental feature flag until kernel improvements to the gpio-aggreagtor lands. Signed-off-by: Zeyad Gouda <[email protected]>

strutil: add range parsing helper

3b8736f

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! i/builtin: use strutil.ParseRange helper

47528af

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! i/builtin: add source-chip validation

5e0f46b

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! strutil: typo fix and test coverage improvement

f140b66

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! i/builtin: use dirs.DistroLibExecDir instead of fixed path

c631204

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! i/builtin: fix release info mocking order

795a6cd

Signed-off-by: Zeyad Gouda <[email protected]>

tests: exclude gpio-chardev interface from document-interfaces-url

422ca70

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! address review comments

84208f2

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! strutil: simplify Range into a slice of RangeSpan

8092b3e

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! many: address review comments

4b5331e

Signed-off-by: Zeyad Gouda <[email protected]>

fixup! i/builtin: fix typo of plug name using slot name

96e9663

Signed-off-by: Zeyad Gouda <[email protected]>

ZeyadYasser force-pushed the gpiod-chardev-interface branch from b80228a to 96e9663 Compare March 26, 2025 09:20

ernestl merged commit 1c897a0 into canonical:master Mar 26, 2025
70 of 75 checks passed

i/builtin: add gpio-chardev interface #15172

i/builtin: add gpio-chardev interface #15172

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