core: add gpiod_request_lines

PATCH In review Kent Gibson 2 participants 7 messages Mar 31, 2022 – Apr 4, 2022

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Kent Gibson

author

2022-03-31 01:12 UTC #0 lore raw

v2 cover core: add gpiod_request_lines

In my review of the CXX bindings I suggested a top-level version of Chip.request_lines(), and possibly a C API version as well, so here is the C version, plus a couple of semi-related tweaks I made along the way.

The first patch adds the gpiod_request_lines().
Patch 3 migrates the appropriate tools.
Patch 4 minimizes the lifetimes of objects in the tools as I've previously seen confusion over how long lived objects need to be. Patch 2 is just a rename cos "inexistent" looks weird to me. Strictly speaking it is fine, but unless there is a problem with using "nonexistent" I would go with the latter.

This series may be require my unsigned values patch.

Cheers,
Kent.

Kent Gibson (4):
core: add gpiod_request_lines
tools: rename inexistent to nonexistent
tools: migrate to gpiod_request_lines
tools: minimize object lifetimes

 include/gpiod.h            | 15 ++++++++
 lib/line-request.c         | 17 +++++++++
 tests/tests-line-request.c | 73 ++++++++++++++++++++++++++++++++++++++
 tools/gpio-tools-test.bats |  4 +--
 tools/gpiodetect.c         |  2 +-
 tools/gpiofind.c           |  2 +-
 tools/gpioget.c            | 25 +++++++------
 tools/gpioinfo.c           |  4 +--
 tools/gpiomon.c            | 16 ++++-----
 tools/gpioset.c            | 18 +++++-----
 tools/tools-common.c       | 50 ++++++++++----------------
 tools/tools-common.h       |  5 +--
 12 files changed, 164 insertions(+), 67 deletions(-)

Signature · 1 line

2.35.1

Kent Gibson

author

2022-03-31 01:12 UTC #1 lore raw

PATCH v2 1/4 core: add gpiod_request_lines

Add a wrapper around gpiod_chip_open() and gpiod_chip_request_lines() for the common use case of only requesting a single set of lines from a chip. The chip itself is only required for the request so hide it from the user.

Signed-off-by Kent Gibson<[email protected]>

---
 include/gpiod.h            | 15 ++++++++
 lib/line-request.c         | 17 +++++++++
 tests/tests-line-request.c | 73 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 105 insertions(+)

include/gpiod.h +15 -0

index 456c2b8..8f64d7f 100644
@@ -50,6 +50,21 @@ struct gpiod_info_event;
 struct gpiod_edge_event;
 struct gpiod_edge_event_buffer;
 
+/**
+ * @brief Request a set of lines for exclusive usage.
+ * @param path GPIO chip path.
+ * @param req_cfg Request config object.
+ * @param line_cfg Line config object.
+ * @return New line request object or NULL if an error occurred. The request
+ *	   must be released by the caller using ::gpiod_line_request_release.
+ * @note Line configuration overrides for lines that are not requested are
+ *	 silently ignored.
+ */
+struct gpiod_line_request *
+gpiod_request_lines(const char *path,
+		    struct gpiod_request_config *req_cfg,
+		    struct gpiod_line_config *line_cfg);
+
 /**
  * @defgroup chips GPIO chips
  * @{

lib/line-request.c +17 -0

index d578a9e..639a66f 100644
@@ -16,6 +16,23 @@ struct gpiod_line_request {
 	int fd;
 };
 
+GPIOD_API struct gpiod_line_request *
+gpiod_request_lines(const char *path,
+		    struct gpiod_request_config *req_cfg,
+		    struct gpiod_line_config *line_cfg)
+{
+	struct gpiod_chip *chip;
+	struct gpiod_line_request *request;
+
+	chip = gpiod_chip_open(path);
+	if (chip == NULL)
+		return NULL;
+
+	request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);
+	gpiod_chip_close(chip);
+	return request;
+}
+
 struct gpiod_line_request *
 gpiod_line_request_from_uapi(struct gpio_v2_line_request *uapi_req)
 {

tests/tests-line-request.c +73 -0

79 lines not on this page · raw message

Signature · 1 line

2.35.1

Kent Gibson

author

2022-03-31 01:12 UTC #2 lore raw

PATCH v2 2/4 tools: rename inexistent to nonexistent

In reply to Kent Gibson

The use of inexistent is virtually nonexistent, so switch to the more usual form.

Signed-off-by Kent Gibson <[email protected]>

---
 tools/gpio-tools-test.bats | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

tools/gpio-tools-test.bats +2 -2

index 69ad786..32c3861 100755
@@ -309,8 +309,8 @@ teardown() {
 	assert_fail output_regex_match "\\s+line\\s+7:\\s+unnamed\\s+unused\\s+input\\s+active-high"
 }
 
-@test "gpioinfo: inexistent chip" {
-	run_tool gpioinfo "inexistent"
+@test "gpioinfo: nonexistent chip" {
+	run_tool gpioinfo "nonexistent"
 
 	test "$status" -eq 1
 }

Signature · 1 line

2.35.1

Kent Gibson

author

2022-03-31 01:13 UTC #3 lore raw

PATCH v2 3/4 tools: migrate to gpiod_request_lines

In reply to Kent Gibson

Switch to gpiod_request_lines() for tools that only use the chip to request lines.

Signed-off-by Kent Gibson <[email protected]>

---
 tools/gpiodetect.c   |  2 +-
 tools/gpiofind.c     |  2 +-
 tools/gpioget.c      | 11 +++++-----
 tools/gpioinfo.c     |  4 ++--
 tools/gpiomon.c      | 11 +++++-----
 tools/gpioset.c      | 11 +++++-----
 tools/tools-common.c | 50 +++++++++++++++++---------------------------
 tools/tools-common.h |  5 +++--
 8 files changed, 41 insertions(+), 55 deletions(-)

tools/gpiodetect.c +1 -1

index 8f6e8b3..2fada05 100644
@@ -67,7 +67,7 @@ int main(int argc, char **argv)
 		die_perror("unable to scan /dev");
 
 	for (i = 0; i < num_chips; i++) {
-		chip = chip_open_by_name(entries[i]->d_name);
+		chip = chip_open(chip_path_from_name(entries[i]->d_name));
 		if (!chip)
 			die_perror("unable to open %s", entries[i]->d_name);

tools/gpiofind.c +1 -1

index 36eba86..17e1702 100644
@@ -67,7 +67,7 @@ int main(int argc, char **argv)
 		die_perror("unable to scan /dev");
 
 	for (i = 0; i < num_chips; i++) {
-		chip = chip_open_by_name(entries[i]->d_name);
+		chip = chip_open(chip_path_from_name(entries[i]->d_name));
 		if (!chip) {
 			if (errno == EACCES)
 				continue;

tools/gpioget.c +5 -6

index 2cf5eae..f4c5d46 100644
@@ -46,11 +46,10 @@ int main(int argc, char **argv)
 	struct gpiod_request_config *req_cfg;
 	struct gpiod_line_request *request;
 	struct gpiod_line_config *line_cfg;
-	struct gpiod_chip *chip;
 	bool active_low = false;
 	unsigned int *offsets, *values;
 	size_t i, num_lines;
-	char *device, *end;
+	char *device, *end, *path;
 
 	for (;;) {
 		optc = getopt_long(argc, argv, shortopts, longopts, &opti);

@@ -103,8 +102,8 @@ int main(int argc, char **argv)
 			die("invalid GPIO offset: %s", argv[i + 1]);
 	}
 
-	chip = chip_open_lookup(device);
-	if (!chip)
+	path = chip_path_lookup(device);
+	if (!path)
 		die_perror("unable to open %s", device);
 
 	line_cfg = gpiod_line_config_new();

@@ -126,7 +125,7 @@ int main(int argc, char **argv)
 	gpiod_request_config_set_consumer(req_cfg, "gpioget");
 	gpiod_request_config_set_offsets(req_cfg, num_lines, offsets);
 
-	request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);
+	request = gpiod_request_lines(path, req_cfg, line_cfg);
 	if (!request)
 		die_perror("unable to request lines");

@@ -144,7 +143,7 @@ int main(int argc, char **argv)
 	gpiod_line_request_release(request);
 	gpiod_request_config_free(req_cfg);
 	gpiod_line_config_free(line_cfg);
-	gpiod_chip_close(chip);
+	free(path);
 	free(offsets);
 	free(values);

tools/gpioinfo.c +2 -2

index fbe2a13..f0f9926 100644
@@ -227,7 +227,7 @@ int main(int argc, char **argv)
 			die_perror("unable to scan /dev");
 
 		for (i = 0; i < num_chips; i++) {
-			chip = chip_open_by_name(entries[i]->d_name);
+			chip = chip_open(chip_path_from_name(entries[i]->d_name));
 			if (!chip)
 				die_perror("unable to open %s",
 					   entries[i]->d_name);

@@ -240,7 +240,7 @@ int main(int argc, char **argv)
 		free(entries);
 	} else {
 		for (i = 0; i < argc; i++) {
-			chip = chip_open_lookup(argv[i]);
+			chip = chip_open(chip_path_lookup(argv[i]));
 			if (!chip)
 				die_perror("looking up chip %s", argv[i]);

tools/gpiomon.c +5 -6

index f6a0dba..e461458 100644
@@ -164,9 +164,8 @@ int main(int argc, char **argv)
 	struct gpiod_line_config *line_cfg;
 	unsigned int offsets[64], offset;
 	struct gpiod_edge_event *event;
-	struct gpiod_chip *chip;
 	struct mon_ctx ctx;
-	char *end;
+	char *end, *path;
 
 	/*
 	 * FIXME: use signalfd once the API has been converted to using a single file

@@ -250,8 +249,8 @@ int main(int argc, char **argv)
 		num_lines++;
 	}
 
-	chip = chip_open_lookup(argv[0]);
-	if (!chip)
+	path = chip_path_lookup(argv[0]);
+	if (!path)
 		die_perror("unable to open %s", argv[0]);
 
 	line_cfg = gpiod_line_config_new();

@@ -271,7 +270,7 @@ int main(int argc, char **argv)
 	gpiod_request_config_set_consumer(req_cfg, "gpiomon");
 	gpiod_request_config_set_offsets(req_cfg, num_lines, offsets);
 
-	request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);
+	request = gpiod_request_lines(path, req_cfg, line_cfg);
 	if (!request)
 		die_perror("unable to request lines");

@@ -314,7 +313,7 @@ done:
 	gpiod_line_request_release(request);
 	gpiod_request_config_free(req_cfg);
 	gpiod_line_config_free(line_cfg);
-	gpiod_chip_close(chip);
+	free(path);
 
 	return EXIT_SUCCESS;
 }

tools/gpioset.c +5 -6

index 1c11470..7497eab 100644
@@ -195,11 +195,10 @@ int main(int argc, char **argv)
 	struct gpiod_line_request *request;
 	struct gpiod_line_config *line_cfg;
 	struct callback_data cbdata;
-	struct gpiod_chip *chip;
 	bool active_low = false;
 	unsigned int *offsets, *values;
 	size_t i, num_lines;
-	char *device, *end;
+	char *device, *end, *path;
 
 	memset(&cbdata, 0, sizeof(cbdata));

@@ -288,8 +287,8 @@ int main(int argc, char **argv)
 			die("invalid offset: %s", argv[i + 1]);
 	}
 
-	chip = chip_open_lookup(device);
-	if (!chip)
+	path = chip_path_lookup(device);
+	if (!path)
 		die_perror("unable to open %s", device);
 
 	line_cfg = gpiod_line_config_new();

@@ -314,7 +313,7 @@ int main(int argc, char **argv)
 	gpiod_request_config_set_consumer(req_cfg, "gpioset");
 	gpiod_request_config_set_offsets(req_cfg, num_lines, offsets);
 
-	request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);
+	request = gpiod_request_lines(path, req_cfg, line_cfg);
 	if (!request)
 		die_perror("unable to request lines");

@@ -324,7 +323,7 @@ int main(int argc, char **argv)
 	gpiod_line_request_release(request);
 	gpiod_request_config_free(req_cfg);
 	gpiod_line_config_free(line_cfg);
-	gpiod_chip_close(chip);
+	free(path);
 	free(offsets);
 
 	return EXIT_SUCCESS;

tools/tools-common.c +19 ~~-31~~

73 lines not on this page · raw message

tools/tools-common.h +3 -2

index f059440..d0b3a83 100644
@@ -29,7 +29,8 @@ int parse_bias(const char *option);
 void print_bias_help(void);
 int make_signalfd(void);
 int chip_dir_filter(const struct dirent *entry);
-struct gpiod_chip *chip_open_by_name(const char *name);
-struct gpiod_chip *chip_open_lookup(const char *device);
+struct gpiod_chip *chip_open(const char *path);
+char *chip_path_from_name(const char *name);
+char *chip_path_lookup(const char *device);
 
 #endif /* __GPIOD_TOOLS_COMMON_H__ */

Signature · 1 line

2.35.1

Kent Gibson

author

2022-03-31 01:13 UTC #4 lore raw

PATCH v2 4/4 tools: minimize object lifetimes

In reply to Kent Gibson

The tools double as examples of API usage, so keep object lifetimes to a minimum to highlight where transient objects are no longer required and may be discarded.

Signed-off-by Kent Gibson <[email protected]>

---
 tools/gpioget.c | 16 ++++++++++------
 tools/gpiomon.c |  7 ++++---
 tools/gpioset.c |  9 +++++----
 3 files changed, 19 insertions(+), 13 deletions(-)

tools/gpioget.c +10 -6

index f4c5d46..f789198 100644
@@ -92,8 +92,7 @@ int main(int argc, char **argv)
 	num_lines = argc - 1;
 
 	offsets = calloc(num_lines, sizeof(*offsets));
-	values = calloc(num_lines, sizeof(*values));
-	if (!offsets || ! values)
+	if (!offsets)
 		die("out of memory");
 
 	for (i = 0; i < num_lines; i++) {

@@ -124,11 +123,20 @@ int main(int argc, char **argv)
 
 	gpiod_request_config_set_consumer(req_cfg, "gpioget");
 	gpiod_request_config_set_offsets(req_cfg, num_lines, offsets);
+	free(offsets);
 
 	request = gpiod_request_lines(path, req_cfg, line_cfg);
 	if (!request)
 		die_perror("unable to request lines");
 
+	free(path);
+	gpiod_request_config_free(req_cfg);
+	gpiod_line_config_free(line_cfg);
+
+	values = calloc(num_lines, sizeof(*values));
+	if (!values)
+		die("out of memory");
+
 	ret = gpiod_line_request_get_values(request, values);
 	if (ret)
 		die_perror("unable to read GPIO line values");

@@ -141,10 +149,6 @@ int main(int argc, char **argv)
 	printf("\n");
 
 	gpiod_line_request_release(request);
-	gpiod_request_config_free(req_cfg);
-	gpiod_line_config_free(line_cfg);
-	free(path);
-	free(offsets);
 	free(values);
 
 	return EXIT_SUCCESS;

tools/gpiomon.c +4 -3

index e461458..34de2b2 100644
@@ -274,6 +274,10 @@ int main(int argc, char **argv)
 	if (!request)
 		die_perror("unable to request lines");
 
+	free(path);
+	gpiod_request_config_free(req_cfg);
+	gpiod_line_config_free(line_cfg);
+
 	event_buffer = gpiod_edge_event_buffer_new(EVENT_BUF_SIZE);
 	if (!event_buffer)
 		die_perror("unable to allocate the line event buffer");

@@ -311,9 +315,6 @@ int main(int argc, char **argv)
 done:
 	gpiod_edge_event_buffer_free(event_buffer);
 	gpiod_line_request_release(request);
-	gpiod_request_config_free(req_cfg);
-	gpiod_line_config_free(line_cfg);
-	free(path);
 
 	return EXIT_SUCCESS;
 }

tools/gpioset.c +5 -4

index 7497eab..f28f8b6 100644
@@ -312,19 +312,20 @@ int main(int argc, char **argv)
 
 	gpiod_request_config_set_consumer(req_cfg, "gpioset");
 	gpiod_request_config_set_offsets(req_cfg, num_lines, offsets);
+	free(offsets);
 
 	request = gpiod_request_lines(path, req_cfg, line_cfg);
 	if (!request)
 		die_perror("unable to request lines");
 
+	free(path);
+	gpiod_request_config_free(req_cfg);
+	gpiod_line_config_free(line_cfg);
+
 	if (mode->callback)
 		mode->callback(&cbdata);
 
 	gpiod_line_request_release(request);
-	gpiod_request_config_free(req_cfg);
-	gpiod_line_config_free(line_cfg);
-	free(path);
-	free(offsets);
 
 	return EXIT_SUCCESS;
 }

Signature · 1 line

2.35.1

Bartosz Golaszewski

2022-04-02 12:47 UTC #5 lore raw

In reply to Kent Gibson

Quoted 39 lines · Kent Gibson

In my review of the CXX bindings I suggested a top-level version of Chip.request_lines(), and possibly a C API version as well, so here is the C version, plus a couple of semi-related tweaks I made along the way.
The first patch adds the gpiod_request_lines().
Patch 3 migrates the appropriate tools.
Patch 4 minimizes the lifetimes of objects in the tools as I've previously seen confusion over how long lived objects need to be. Patch 2 is just a rename cos "inexistent" looks weird to me. Strictly speaking it is fine, but unless there is a problem with using "nonexistent" I would go with the latter.
This series may be require my unsigned values patch.
Cheers,
Kent.
Kent Gibson (4):
core: add gpiod_request_lines
tools: rename inexistent to nonexistent
tools: migrate to gpiod_request_lines
tools: minimize object lifetimes
 include/gpiod.h            | 15 ++++++++
 lib/line-request.c         | 17 +++++++++
 tests/tests-line-request.c | 73 ++++++++++++++++++++++++++++++++++++++
 tools/gpio-tools-test.bats |  4 +--
 tools/gpiodetect.c         |  2 +-
 tools/gpiofind.c           |  2 +-
 tools/gpioget.c            | 25 +++++++------
 tools/gpioinfo.c           |  4 +--
 tools/gpiomon.c            | 16 ++++-----
 tools/gpioset.c            | 18 +++++-----
 tools/tools-common.c       | 50 ++++++++++----------------
 tools/tools-common.h       |  5 +--
 12 files changed, 164 insertions(+), 67 deletions(-)

Quoted 3 lines

--
2.35.1

Ugh, I didn't respond under the C++ review in time before you spent time on this. :/

I don't agree with this change. For C API I think the intention for v2 was to avoid having all kinds of high-level helpers and limit the number of functions to only those that are necessary to fully leverage the kernel uAPI and this one isn't necessary. I think we discussed it multiple times and agreed that the C library needs to be minimal this time.

For C++ and Python the issue is irrelevant because you can do:

auto request = gpiod::Chip("/dev/gpiochip0").request_lines(req_cfg, line_cfg);

request = gpiod.Chip("/dev/gpiochip0").request_lines(req_cfg, line_cfg)

respectively and achieve the same result while still using a one-liner.

Unless there's a *really* good reason to do this, it's a NAK from my side.

Bart

Kent Gibson

author

2022-04-04 09:54 UTC #6 lore raw

Quoted 40 lines · Bartosz Golaszewski

Quoted 39 lines · Kent Gibson
In my review of the CXX bindings I suggested a top-level version of Chip.request_lines(), and possibly a C API version as well, so here is the C version, plus a couple of semi-related tweaks I made along the way.
The first patch adds the gpiod_request_lines().
Patch 3 migrates the appropriate tools.
Patch 4 minimizes the lifetimes of objects in the tools as I've previously seen confusion over how long lived objects need to be. Patch 2 is just a rename cos "inexistent" looks weird to me. Strictly speaking it is fine, but unless there is a problem with using "nonexistent" I would go with the latter.
This series may be require my unsigned values patch.
Cheers,
Kent.
Kent Gibson (4):
core: add gpiod_request_lines
tools: rename inexistent to nonexistent
tools: migrate to gpiod_request_lines
tools: minimize object lifetimes
 include/gpiod.h            | 15 ++++++++
 lib/line-request.c         | 17 +++++++++
 tests/tests-line-request.c | 73 ++++++++++++++++++++++++++++++++++++++
 tools/gpio-tools-test.bats |  4 +--
 tools/gpiodetect.c         |  2 +-
 tools/gpiofind.c           |  2 +-
 tools/gpioget.c            | 25 +++++++------
 tools/gpioinfo.c           |  4 +--
 tools/gpiomon.c            | 16 ++++-----
 tools/gpioset.c            | 18 +++++-----
 tools/tools-common.c       | 50 ++++++++++----------------
 tools/tools-common.h       |  5 +--
 12 files changed, 164 insertions(+), 67 deletions(-)

Quoted 7 lines

Quoted 3 lines
--
2.35.1
Ugh, I didn't respond under the C++ review in time before you spent time on this. :/

Not a problem - it was just something to fill in time.

Quoted 7 lines

I don't agree with this change. For C API I think the intention for v2 was to avoid having all kinds of high-level helpers and limit the number of functions to only those that are necessary to fully leverage the kernel uAPI and this one isn't necessary. I think we discussed it multiple times and agreed that the C library needs to be minimal this time.

Quoted 8 lines

For C++ and Python the issue is irrelevant because you can do:
auto request = gpiod::Chip("/dev/gpiochip0").request_lines(req_cfg, line_cfg);
or
request = gpiod.Chip("/dev/gpiochip0").request_lines(req_cfg, line_cfg)

The point isn't being able to do a one liner, the point is to remove the chip object from the set of concerns for the basic use case, and so provide an easier on-ramp for the casual user.

Quoted 4 lines

respectively and achieve the same result while still using a one-liner.
Unless there's a *really* good reason to do this, it's a NAK from my side.

That's fine.

Cheers,
Kent.