Merge #67

67: Add PEC management support for SMBus compatible controller. r=eldruin a=hilt0n

Thanks for the review!

Some cleaning and updated the changelog.
r? `@eldruin`

Co-authored-by: Yannick Lanz <yannick.lanz@wifx.net>

Author: bors[bot]

CHANGELOG.md

@@ -9,6 +9,7 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 ## [Unreleased]
 
 - Updated nix to allow both version `0.22` or `0.23`.
+- Add PEC support for SMBus compatible adapters
 
 ## [v0.5.0] - 2021-09-21
 

src/ffi.rs

@@ -153,9 +153,10 @@ pub struct i2c_rdwr_ioctl_data {
 mod ioctl {
     pub use super::i2c_rdwr_ioctl_data;
     pub use super::i2c_smbus_ioctl_data;
-    use super::{I2C_RDWR, I2C_SLAVE, I2C_SMBUS};
+    use super::{I2C_PEC, I2C_RDWR, I2C_SLAVE, I2C_SMBUS};
 
     ioctl_write_int_bad!(set_i2c_slave_address, I2C_SLAVE);
+    ioctl_write_int_bad!(set_smbus_pec, I2C_PEC);
     ioctl_write_ptr_bad!(i2c_smbus, I2C_SMBUS, i2c_smbus_ioctl_data);
     ioctl_write_ptr_bad!(i2c_rdwr, I2C_RDWR, i2c_rdwr_ioctl_data);
 }
@@ -167,6 +168,13 @@ pub fn i2c_set_slave_address(fd: RawFd, slave_address: u16) -> Result<(), nix::E
     Ok(())
 }
 
+pub fn i2c_set_smbus_pec(fd: RawFd, enable: bool) -> Result<(), nix::Error> {
+    unsafe {
+        ioctl::set_smbus_pec(fd, i32::from(enable))?;
+    }
+    Ok(())
+}
+
 unsafe fn i2c_smbus_access(
     fd: RawFd,
     read_write: I2CSMBusReadWrite,

src/linux.rs

@@ -25,6 +25,7 @@ pub use core::I2CMessage;
 pub struct LinuxI2CDevice {
     devfile: File,
     slave_address: u16,
+    pec: bool,
 }
 
 /// Linux I2C bus
@@ -102,8 +103,10 @@ impl LinuxI2CDevice {
         let mut device = LinuxI2CDevice {
             devfile: file,
             slave_address: 0, // will be set later
+            pec: false,
         };
         device.set_slave_address(slave_address)?;
+        device.set_smbus_pec(false)?;
         Ok(device)
     }
 
@@ -123,6 +126,17 @@ impl LinuxI2CDevice {
         self.slave_address = slave_address;
         Ok(())
     }
+
+    /// Enable/Disable PEC support for this device
+    ///
+    /// Used only for SMBus transactions.  This request only has an effect if the
+    /// the adapter has I2C_FUNC_SMBUS_PEC; it is still safe if not, it just
+    /// doesn't have any effect.
+    pub fn set_smbus_pec(&mut self, enable: bool) -> Result<(), LinuxI2CError> {
+        ffi::i2c_set_smbus_pec(self.as_raw_fd(), enable)?;
+        self.pec = enable;
+        Ok(())
+    }
 }
 
 impl I2CDevice for LinuxI2CDevice {