[PATCH v5 1/2] i2c-tools: Allow passing device file paths

[Brigham Campbell <me@brighamcampbell.com>]

Make i2c-tools binaries accept a device file path or symlink directly.
This is useful, for example, for use with stable symlinks generated by
udev.

In the case of conflict, the bus parameter is parsed with the following
precedence in order to maintain backwards compatibility:

number -> name -> device path

Suggested-by: Gero Schwäricke <gero.schwaericke@sevenlab.de>
Signed-off-by: Brigham Campbell <me@brighamcampbell.com>
---
 tools/i2cbusses.c   | 127 ++++++++++++++++++++++++++++++----------------------
 tools/i2cbusses.h   |   3 +-
 tools/i2cdetect.c   |  12 ++---
 tools/i2cdump.c     |  12 ++---
 tools/i2cget.c      |  11 ++---
 tools/i2cset.c      |  11 ++---
 tools/i2ctransfer.c |  11 ++---
 7 files changed, 95 insertions(+), 92 deletions(-)

diff --git a/tools/i2cbusses.c b/tools/i2cbusses.c
index d687615..40d863f 100644
--- a/tools/i2cbusses.c
+++ b/tools/i2cbusses.c
@@ -58,6 +58,42 @@ static struct adap_type adap_types[5] = {
 	  .algo		= "N/A", },
 };
 
+static int open_i2c_dev_by_nr(int i2cbus, char *filename, size_t size, int quiet)
+{
+	int file, len;
+
+	len = snprintf(filename, size, "/dev/i2c/%d", i2cbus);
+	if (len >= (int)size) {
+		fprintf(stderr, "%s: path truncated\n", filename);
+		return -EOVERFLOW;
+	}
+	file = open(filename, O_RDWR);
+
+	if (file < 0 && (errno == ENOENT || errno == ENOTDIR)) {
+		len = snprintf(filename, size, "/dev/i2c-%d", i2cbus);
+		if (len >= (int)size) {
+			fprintf(stderr, "%s: path truncated\n", filename);
+			return -EOVERFLOW;
+		}
+		file = open(filename, O_RDWR);
+	}
+
+	if (file < 0 && !quiet) {
+		if (errno == ENOENT) {
+			fprintf(stderr, "Error: Could not open file "
+				"`/dev/i2c-%d' or `/dev/i2c/%d': %s\n",
+				i2cbus, i2cbus, strerror(ENOENT));
+		} else {
+			fprintf(stderr, "Error: Could not open file "
+				"`%s': %s\n", filename, strerror(errno));
+			if (errno == EACCES)
+				fprintf(stderr, "Run as root?\n");
+		}
+	}
+
+	return file;
+}
+
 static enum adt i2c_get_funcs(int i2cbus)
 {
 	unsigned long funcs;
@@ -65,7 +101,7 @@ static enum adt i2c_get_funcs(int i2cbus)
 	char filename[20];
 	enum adt ret;
 
-	file = open_i2c_dev(i2cbus, filename, sizeof(filename), 1);
+	file = open_i2c_dev_by_nr(i2cbus, filename, sizeof(filename), 1);
 	if (file < 0)
 		return adt_unknown;
 
@@ -348,37 +384,11 @@ static int lookup_i2c_bus_by_name(const char *bus_name)
 		}
 	}
 
-	if (i2cbus == -1)
-		fprintf(stderr, "Error: I2C bus name doesn't match any "
-			"bus present!\n");
-
 done:
 	free_adapters(adapters);
 	return i2cbus;
 }
 
-/*
- * Parse an I2CBUS command line argument and return the corresponding
- * bus number, or a negative value if the bus is invalid.
- */
-int lookup_i2c_bus(const char *i2cbus_arg)
-{
-	unsigned long i2cbus;
-	char *end;
-
-	i2cbus = strtoul(i2cbus_arg, &end, 0);
-	if (*end || !*i2cbus_arg) {
-		/* Not a number, maybe a name? */
-		return lookup_i2c_bus_by_name(i2cbus_arg);
-	}
-	if (i2cbus > 0xFFFFF) {
-		fprintf(stderr, "Error: I2C bus out of range!\n");
-		return -2;
-	}
-
-	return i2cbus;
-}
-
 /*
  * Parse a CHIP-ADDRESS command line argument and return the corresponding
  * chip address, or a negative value if the address is invalid.
@@ -410,39 +420,50 @@ int parse_i2c_address(const char *address_arg, int all_addrs)
 	return address;
 }
 
-int open_i2c_dev(int i2cbus, char *filename, size_t size, int quiet)
+/*
+ * Parse a I2CBUS command line argument and return the corresponding file
+ * descriptor, or a negative value if the file can't be resolved. Use *filename
+ * to return the file path. size refers to the size of the buffer which
+ * **filename initially points to.
+ *
+ * For historical reasons, I2CBUS parsing precedence is as follows:
+ * 	number -> name -> device path
+ */
+int open_i2c_dev(char *i2cbus_arg, char **filename, size_t size, int quiet)
 {
-	int file, len;
+	int file, i2cbus;
+	unsigned long i2cbus_ul;
+	char *end;
 
-	len = snprintf(filename, size, "/dev/i2c/%d", i2cbus);
-	if (len >= (int)size) {
-		fprintf(stderr, "%s: path truncated\n", filename);
-		return -EOVERFLOW;
-	}
-	file = open(filename, O_RDWR);
-
-	if (file < 0 && (errno == ENOENT || errno == ENOTDIR)) {
-		len = snprintf(filename, size, "/dev/i2c-%d", i2cbus);
-		if (len >= (int)size) {
-			fprintf(stderr, "%s: path truncated\n", filename);
-			return -EOVERFLOW;
+	i2cbus_ul = strtoul(i2cbus_arg, &end, 0);
+	if (!*end && *i2cbus_arg) {
+		if (i2cbus_ul > 0xFFFFF) {
+			fprintf(stderr, "Error: I2C bus out of range!\n");
+			return -2;
 		}
-		file = open(filename, O_RDWR);
+
+		return open_i2c_dev_by_nr(i2cbus_ul, *filename, size, quiet);
 	}
 
-	if (file < 0 && !quiet) {
-		if (errno == ENOENT) {
-			fprintf(stderr, "Error: Could not open file "
-				"`/dev/i2c-%d' or `/dev/i2c/%d': %s\n",
-				i2cbus, i2cbus, strerror(ENOENT));
-		} else {
-			fprintf(stderr, "Error: Could not open file "
-				"`%s': %s\n", filename, strerror(errno));
-			if (errno == EACCES)
-				fprintf(stderr, "Run as root?\n");
-		}
+	i2cbus = lookup_i2c_bus_by_name(i2cbus_arg);
+	if (i2cbus >= 0) {
+		return open_i2c_dev_by_nr(i2cbus, *filename, size, quiet);
 	}
 
+	*filename = i2cbus_arg;
+	file = open(i2cbus_arg, O_RDWR);
+
+	if (file >= 0 || quiet) return file;
+
+	if (errno == EACCES) {
+		fprintf(stderr, "Error: Could not open file `%s': %s\n"
+			"Run as root?\n", i2cbus_arg, strerror(errno));
+		return file;
+	}
+
+	fprintf(stderr, "Error: Couldn't interpret `%s' as a bus number, "
+		"name, or device file path!\n", i2cbus_arg);
+
 	return file;
 }
 
diff --git a/tools/i2cbusses.h b/tools/i2cbusses.h
index 6f901b6..0cec50f 100644
--- a/tools/i2cbusses.h
+++ b/tools/i2cbusses.h
@@ -29,9 +29,8 @@ struct i2c_adap {
 struct i2c_adap *gather_i2c_busses(void);
 void free_adapters(struct i2c_adap *adapters);
 
-int lookup_i2c_bus(const char *i2cbus_arg);
 int parse_i2c_address(const char *address_arg, int all_addrs);
-int open_i2c_dev(int i2cbus, char *filename, size_t size, int quiet);
+int open_i2c_dev(char *i2cbus_arg, char **filename, size_t size, int quiet);
 int set_slave_addr(int file, int address, int force);
 
 #define MISSING_FUNC_FMT	"Error: Adapter does not have %s capability\n"
diff --git a/tools/i2cdetect.c b/tools/i2cdetect.c
index 3c22f17..b62f395 100644
--- a/tools/i2cdetect.c
+++ b/tools/i2cdetect.c
@@ -213,8 +213,9 @@ static void print_i2c_busses(void)
 int main(int argc, char *argv[])
 {
 	char *end;
-	int i2cbus, file, res;
-	char filename[20];
+	int file, res;
+	char filename_buf[20];
+	char *filename = filename_buf;
 	unsigned long funcs;
 	int mode = MODE_AUTO;
 	int first = 0x08, last = 0x77;
@@ -277,11 +278,6 @@ int main(int argc, char *argv[])
 		help();
 		exit(1);
 	}
-	i2cbus = lookup_i2c_bus(argv[optind]);
-	if (i2cbus < 0) {
-		help();
-		exit(1);
-	}
 
 	/* read address range if present */
 	if (argc == optind + 3 && mode != MODE_FUNC) {
@@ -321,7 +317,7 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
-	file = open_i2c_dev(i2cbus, filename, sizeof(filename), 0);
+	file = open_i2c_dev(argv[optind], &filename, sizeof(filename_buf), 0);
 	if (file < 0) {
 		exit(1);
 	}
diff --git a/tools/i2cdump.c b/tools/i2cdump.c
index d315e2f..ce3be2c 100644
--- a/tools/i2cdump.c
+++ b/tools/i2cdump.c
@@ -100,9 +100,10 @@ static int check_funcs(int file, int size, int pec)
 int main(int argc, char *argv[])
 {
 	char *end;
-	int i, j, res, i2cbus, address, size, file;
+	int i, j, res, address, size, file;
 	int bank = 0, bankreg = 0x4E, old_bank = 0;
-	char filename[20];
+	char filename_buf[20];
+	char *filename = filename_buf;
 	int block[256];
 	int pec = 0, even = 0;
 	int opt;
@@ -135,11 +136,6 @@ int main(int argc, char *argv[])
 		help();
 		exit(1);
 	}
-	i2cbus = lookup_i2c_bus(argv[optind]);
-	if (i2cbus < 0) {
-		help();
-		exit(1);
-	}
 
 	if (argc < optind + 2) {
 		fprintf(stderr, "Error: No address specified!\n");
@@ -235,7 +231,7 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	file = open_i2c_dev(i2cbus, filename, sizeof(filename), 0);
+	file = open_i2c_dev(argv[optind], &filename, sizeof(filename_buf), 0);
 	if (file < 0
 	 || check_funcs(file, size, pec)
 	 || set_slave_addr(file, address, force))
diff --git a/tools/i2cget.c b/tools/i2cget.c
index 17d78bf..e08ee81 100644
--- a/tools/i2cget.c
+++ b/tools/i2cget.c
@@ -169,9 +169,10 @@ static int confirm(const char *filename, int address, int size, int daddress,
 int main(int argc, char *argv[])
 {
 	char *end;
-	int res, i2cbus, address, size, file;
+	int res, address, size, file;
 	int daddress;
-	char filename[20];
+	char filename_buf[20];
+	char *filename = filename_buf;
 	int pec = 0;
 	int opt;
 	int force = 0, yes = 0, version = 0, all_addrs = 0;
@@ -199,10 +200,6 @@ int main(int argc, char *argv[])
 	if (argc < optind + 2)
 		help(1);
 
-	i2cbus = lookup_i2c_bus(argv[optind]);
-	if (i2cbus < 0)
-		help(1);
-
 	address = parse_i2c_address(argv[optind+1], all_addrs);
 	if (address < 0)
 		help(1);
@@ -251,7 +248,7 @@ int main(int argc, char *argv[])
 		length = I2C_SMBUS_BLOCK_MAX;
 	}
 
-	file = open_i2c_dev(i2cbus, filename, sizeof(filename), 0);
+	file = open_i2c_dev(argv[optind], &filename, sizeof(filename_buf), 0);
 	if (file < 0
 	 || check_funcs(file, size, daddress, pec)
 	 || set_slave_addr(file, address, force))
diff --git a/tools/i2cset.c b/tools/i2cset.c
index aaf7faf..8371570 100644
--- a/tools/i2cset.c
+++ b/tools/i2cset.c
@@ -151,9 +151,10 @@ int main(int argc, char *argv[])
 {
 	char *end;
 	const char *maskp = NULL;
-	int res, i2cbus, address, size, file;
+	int res, address, size, file;
 	int value, daddress, vmask = 0;
-	char filename[20];
+	char filename_buf[20];
+	char *filename = filename_buf;
 	int pec = 0;
 	int opt;
 	int force = 0, yes = 0, version = 0, readback = 0, all_addrs = 0;
@@ -183,10 +184,6 @@ int main(int argc, char *argv[])
 	if (argc < optind + 3)
 		help(1);
 
-	i2cbus = lookup_i2c_bus(argv[optind]);
-	if (i2cbus < 0)
-		help(1);
-
 	address = parse_i2c_address(argv[optind+1], all_addrs);
 	if (address < 0)
 		help(1);
@@ -301,7 +298,7 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	file = open_i2c_dev(i2cbus, filename, sizeof(filename), 0);
+	file = open_i2c_dev(argv[optind], &filename, sizeof(filename_buf), 0);
 	if (file < 0
 	 || check_funcs(file, size, pec)
 	 || set_slave_addr(file, address, force))
diff --git a/tools/i2ctransfer.c b/tools/i2ctransfer.c
index a49b734..d9d1396 100644
--- a/tools/i2ctransfer.c
+++ b/tools/i2ctransfer.c
@@ -257,8 +257,9 @@ static enum supported_flags_retval
 
 int main(int argc, char *argv[])
 {
-	char filename[20];
-	int i2cbus, address = -1, file, opt, nmsgs = 0, nmsgs_sent, i;
+	char filename_buf[20];
+	char *filename = filename_buf;
+	int address = -1, file, opt, nmsgs = 0, nmsgs_sent, i;
 	int force = 0, yes = 0, version = 0, verbose = 0, all_addrs = 0, binary = 0;
 	struct i2c_msg msgs[I2C_RDRW_IOCTL_MAX_MSGS];
 	enum parse_state state = PARSE_GET_DESC;
@@ -293,11 +294,7 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
-	i2cbus = lookup_i2c_bus(argv[optind++]);
-	if (i2cbus < 0)
-		exit(1);
-
-	file = open_i2c_dev(i2cbus, filename, sizeof(filename), 0);
+	file = open_i2c_dev(argv[optind++], &filename, sizeof(filename_buf), 0);
 	if (file < 0 || get_funcs(file, &funcs) || check_funcs(funcs))
 		exit(1);
 

-- 
2.55.0