Change in flashrom[master]: lspcon_i2c_spi: support a devpath option

[Peter Marheine (Code Review)]

Peter Marheine has uploaded this change for review. ( https://review.coreboot.org/c/flashrom/+/51967 )

Change subject: lspcon_i2c_spi: support a devpath option
......................................................................

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 that is preferred,
continuing to allow `bus` and requiring 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.

Signed-off-by: Peter Marheine 
Change-Id: Id2adf8a307b9205ce5e5804a6c3e22f19d0c34c9
---
M i2c_helper.h
M i2c_helper_linux.c
M lspcon_i2c_spi.c
3 files changed, 46 insertions(+), 23 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/67/51967/1

diff --git a/i2c_helper.h b/i2c_helper.h
index 599e08b..cab2ce6 100644
--- a/i2c_helper.h
+++ b/i2c_helper.h
@@ -72,6 +72,14 @@
 int i2c_open(int bus, uint16_t addr, int force);

/**
+ * i2c_open_path: open an I2C device by device path
+ *
+ * This function behaves the same as i2c_open, but takes a filesystem
+ * path (assumed to be an I2C device file) instead of a bus number.
+ */
+int i2c_open_path(const char *path, uint16_t addr, int force);
+
+/**
  * i2c_close - closes the file descriptor returned by i2c_open
  *
  * @fd:	file descriptor to be closed.
diff --git a/i2c_helper_linux.c b/i2c_helper_linux.c
index 5c191f9..10c4547 100644
--- a/i2c_helper_linux.c
+++ b/i2c_helper_linux.c
@@ -36,14 +36,35 @@
    return fd == -1 ? 0 : close(fd);
 }

+int i2c_open_path(const char *path, uint16_t addr, int force)
+{
+	int ret = -1;
+	int fd = open(path, O_RDWR);
+	if (fd < 0) {
+		msg_perr("Unable to open I2C device %s: %s.\n", path, strerror(errno));
+		ret = fd;
+		goto err;
+	}
+
+	int request = force ? I2C_SLAVE_FORCE : I2C_SLAVE;
+	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);
+		goto err;
+	}
+
+err:
+	return ret ? ret : fd;
+}
+
+
 int i2c_open(int bus, uint16_t addr, int force)
 {
    int ret = -1;
-	int fd = -1;

/* Maximum i2c bus number is 255(3 char), +1 for null terminated string. */
    int path_len = strlen(I2C_DEV_PREFIX) + 4;
-	int request = force ? I2C_SLAVE_FORCE : I2C_SLAVE;

if (bus < 0 || bus > I2C_MAX_BUS) {
    	msg_perr("Invalid I2C bus %d.\n", bus);
@@ -63,25 +84,12 @@
    	goto linux_i2c_open_err;
    }

-	fd = open(dev, O_RDWR);
-	if (fd < 0) {
-		msg_perr("Unable to open I2C device %s: %s.\n", dev, strerror(errno));
-		ret = fd;
-		goto linux_i2c_open_err;
-	}
-
-	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);
-		goto linux_i2c_open_err;
-	}
-
+	ret = i2c_open_path(dev, addr, force);
 linux_i2c_open_err:
    if (dev)
    	free(dev);

-	return ret ? ret : fd;
+	return ret;
 }

int i2c_read(int fd, uint16_t addr, i2c_buffer_t *buf)
diff --git a/lspcon_i2c_spi.c b/lspcon_i2c_spi.c
index 7b9f1c0..a748f85 100644
--- a/lspcon_i2c_spi.c
+++ b/lspcon_i2c_spi.c
@@ -434,7 +434,7 @@
 }

/* TODO: remove this out of the specific SPI master implementation. */
-static int get_bus(void)
+static int get_bus_number(void)
 {
    char *bus_str = extract_programmer_param("bus");
         int ret = SPI_GENERIC_ERROR;
@@ -474,16 +474,23 @@

int lspcon_i2c_spi_init(void)
 {
-	int lspcon_i2c_spi_bus = get_bus();
-	if (lspcon_i2c_spi_bus < 0)
+	int fd = -1;
+	char *device_path;
+	int bus_number;
+	if ((device_path = extract_programmer_param("devpath")) != NULL) {
+		fd = i2c_open_path(device_path, REGISTER_ADDRESS, 0);
+		free(device_path);
+	} else if ((bus_number = get_bus_number()) >= 0) {
+		fd = i2c_open(bus_number, REGISTER_ADDRESS, 0);
+	} else {
+		msg_perr("%s: one of devpath or bus must be specified\n", __func__);
    	return SPI_GENERIC_ERROR;
+	}

-	int ret = 0;
-	int fd = i2c_open(lspcon_i2c_spi_bus, REGISTER_ADDRESS, 0);
    if (fd < 0)
    	return fd;

-	ret |= lspcon_i2c_spi_reset_mpu_stop(fd);
+	int ret = lspcon_i2c_spi_reset_mpu_stop(fd);
    if (ret) {
    	msg_perr("%s: call to reset_mpu_stop failed.\n", __func__);
    	return ret;