lspcon_i2c_spi: support a devpath option

Some callers may find it easier to provide the path to an I2C device
at which to communicate with the device, rather than specify the bus
number- doing so might involve trying to parse a path to extract the
number only for flashrom to do the reverse, which is error-prone and
unnecessary.

This change adds support for a `devpath` option, continuing to
allow `bus` and requiring only one of them be specified.

TEST=Verified --flash-size outputs correct values with both
     devpath=/dev/i2c-7 and bus=7, as well as noting that one is
     required if neither is specified and only one may be specified
     if both are given.

Signed-off-by: Peter Marheine <pmarheine@chromium.org>
Change-Id: Id2adf8a307b9205ce5e5804a6c3e22f19d0c34c9
Reviewed-on: https://review.coreboot.org/c/flashrom/+/51967
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 21 insertions, 17 deletions

diff --git a/i2c_helper_linux.c b/i2c_helper_linux.c
index 9383c857..77445052 100644
--- a/i2c_helper_linux.c
+++ b/i2c_helper_linux.c
@@ -37,14 +37,31 @@ int i2c_close(int fd)
 	return fd == -1 ? 0 : close(fd);
 }
 
+int i2c_open_path(const char *path, uint16_t addr, int force)
+{
+	int fd = open(path, O_RDWR);
+	if (fd < 0) {
+		msg_perr("Unable to open I2C device %s: %s.\n", path, strerror(errno));
+		return fd;
+	}
+
+	int request = force ? I2C_SLAVE_FORCE : I2C_SLAVE;
+	int ret = ioctl(fd, request, addr);
+	if (ret < 0) {
+		msg_perr("Unable to set I2C slave address to 0x%02x: %s.\n", addr, strerror(errno));
+		i2c_close(fd);
+                return ret;
+	}
+
+	return fd;
+}
+
+
 int i2c_open(int bus, uint16_t addr, int force)
 {
 	char dev[sizeof(I2C_DEV_PREFIX)] = {0};
 
 	int ret = -1;
-	int fd = -1;
-
-	int request = force ? I2C_SLAVE_FORCE : I2C_SLAVE;
 
 	if (bus < 0 || bus > I2C_MAX_BUS) {
 		msg_perr("Invalid I2C bus %d.\n", bus);
@@ -57,20 +74,7 @@ int i2c_open(int bus, uint16_t addr, int force)
 		return ret;
 	}
 
-	fd = open(dev, O_RDWR);
-	if (fd < 0) {
-		msg_perr("Unable to open I2C device %s: %s.\n", dev, strerror(errno));
-		return fd;
-	}
-
-	ret = ioctl(fd, request, addr);
-	if (ret < 0) {
-		msg_perr("Unable to set I2C slave address to 0x%02x: %s.\n", addr, strerror(errno));
-		i2c_close(fd);
-		return ret;
-	}
-
-	return fd;
+	return i2c_open_path(dev, addr, force);
 }
 
 int i2c_read(int fd, uint16_t addr, i2c_buffer_t *buf)