i2c: Cache adapter functionality
Enhance the I2CDevice class to cache the I2C adapter functionality
value. The adapter functionality value should not change while the
device interface is open.
Caching the functionality value will reduce the number of ioctl() calls
by 50% when doing long sequences of I2C operations.
Tested:
* Verified adapter functionality value is cached
* Verified read() method works on a Witherspoon
* Verified close() method discards the cached functionality value
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: I2b17d91ae4e21aaf52cd4cec9eddb5aab7be37e5
diff --git a/tools/i2c/i2c.cpp b/tools/i2c/i2c.cpp
index 04b9c27..bad5b89 100644
--- a/tools/i2c/i2c.cpp
+++ b/tools/i2c/i2c.cpp
@@ -17,16 +17,24 @@
namespace i2c
{
-void I2CDevice::checkReadFuncs(int type)
+unsigned long I2CDevice::getFuncs()
{
- unsigned long funcs;
-
- /* Check adapter functionality */
- if (ioctl(fd, I2C_FUNCS, &funcs) < 0)
+ // If functionality has not been cached
+ if (cachedFuncs == NO_FUNCS)
{
- throw I2CException("Failed to get funcs", busStr, devAddr, errno);
+ // Get functionality from adapter
+ if (ioctl(fd, I2C_FUNCS, &cachedFuncs) < 0)
+ {
+ throw I2CException("Failed to get funcs", busStr, devAddr, errno);
+ }
}
+ return cachedFuncs;
+}
+
+void I2CDevice::checkReadFuncs(int type)
+{
+ unsigned long funcs = getFuncs();
switch (type)
{
case I2C_SMBUS_BYTE:
@@ -73,14 +81,7 @@
void I2CDevice::checkWriteFuncs(int type)
{
- unsigned long funcs;
-
- /* Check adapter functionality */
- if (ioctl(fd, I2C_FUNCS, &funcs) < 0)
- {
- throw I2CException("Failed to get funcs", busStr, devAddr, errno);
- }
-
+ unsigned long funcs = getFuncs();
switch (type)
{
case I2C_SMBUS_BYTE:
@@ -154,6 +155,7 @@
throw I2CException("Failed to close", busStr, devAddr, errno);
}
fd = INVALID_FD;
+ cachedFuncs = NO_FUNCS;
}
void I2CDevice::read(uint8_t& data)