Add checksum check

src/bin/edidread.rs

@@ -1,8 +1,8 @@
 use clap::Parser;
-use rwedid::args::*;
-use rwedid::i2c::*;
-use rwedid::misc::*;
-use rwedid::std::*;
+use rwedid::args::Args;
+use rwedid::i2c::read_from_bus;
+use rwedid::io::block_by_block_read;
+use rwedid::std::write_to_stdout;
 
 fn main() -> Result<(), std::io::Error> {
     // Parse command line arguments
@@ -14,5 +14,5 @@ fn main() -> Result<(), std::io::Error> {
     })?;
 
     // Write binary blob to stdout
-    write_to_std(&bytes)
+    write_to_stdout(&bytes)
 }

src/bin/edidwrite.rs

@@ -1,16 +1,16 @@
 use clap::Parser;
-use rwedid::args::*;
-use rwedid::i2c::*;
-use rwedid::misc::*;
-use rwedid::std::*;
+use rwedid::args::Args;
+use rwedid::i2c::write_to_bus;
+use rwedid::io::block_by_block_read;
+use rwedid::std::read_from_stdin;
 
 fn main() -> Result<(), std::io::Error> {
     // Parse command line arguments
     let args = Args::parse();
 
-    // Read binary from stdin
-    let data = block_by_block_read(args.blocks, |_, l| read_from_std(l))?;
+    // Read binary blob from stdin
+    let data = block_by_block_read(args.blocks, |_, l| read_from_stdin(l))?;
 
     // Write the data to the chip
-    write_to_bus(&args.device, args.address, data.as_slice())
+    write_to_bus(&args.device, args.address, 0x00, data.as_slice())
 }

src/checksum.rs

@@ -0,0 +1,15 @@
+// Compute and check the checksum over the bytes of a block.
+pub fn checksum(bytes: &[u8]) -> u8 {
+    bytes.iter().fold(0u32, |x, y| x + (*y as u32)) as u8
+}
+
+// Validate the checksum
+pub fn valid_checksum(bytes: &[u8]) -> bool {
+    checksum(bytes) == 0x00
+}
+
+// Print the checksum to stdout
+pub fn print_checksum(bytes: &[u8]) {
+    let cs = checksum(bytes);
+    eprintln!("  Checksum is: {cs}");
+}

src/i2c.rs

@@ -1,6 +1,5 @@
-use i2cdev::core::*;
+use i2cdev::core::{I2CMessage, I2CTransfer};
 use i2cdev::linux::{LinuxI2CDevice, LinuxI2CMessage};
-
 use std::thread;
 use std::time::Duration;
 
@@ -29,19 +28,20 @@ pub fn read_from_bus(
 pub fn write_to_bus(
     i2c_device: &str,
     slave_address: u16,
+    memory_address: u8,
     data: &[u8],
 ) -> Result<(), std::io::Error> {
     let mut dev = LinuxI2CDevice::new(i2c_device, slave_address)?;
 
     // Write 8 bytes at a time
-    for (i, chunk) in data.chunks_exact(8).into_iter().enumerate() {
+    for (i, chunk) in data.chunks_exact(8).enumerate() {
         // Memory address
-        let memory_address: u8 = (i as u8) * 8;
+        let address = memory_address + (i as u8) * 8;
         let mut msgs = [
             // Address to write to
-            LinuxI2CMessage::write(&[memory_address]),
+            LinuxI2CMessage::write(&[address]),
             // Write data to chip
-            LinuxI2CMessage::write(&chunk),
+            LinuxI2CMessage::write(chunk),
         ];
 
         dev.transfer(&mut msgs)?;

src/io.rs

@@ -1,4 +1,6 @@
-// Size of EDID binary block
+use crate::checksum::print_checksum;
+
+/// Size of an EDID block in bytes.
 pub const BLOCK_SIZE: usize = 128;
 
 pub fn block_by_block_read(
@@ -10,22 +12,37 @@ pub fn block_by_block_read(
         None => {
             // Read first block (128 bytes)
             let data_base = read(0x00, BLOCK_SIZE)?;
+            print_checksum(data_base.as_slice());
+
             // Try to read remaining bytes
             let data_extensions = match data_base.len() {
-                // Proper 128 byte block
+                // Proper first block (128 bytes)
                 BLOCK_SIZE => {
                     // Number of extension blocks that should follow
                     let num_extensions: usize = data_base[BLOCK_SIZE - 2].into();
                     // Read remaining blocks
-                    read(BLOCK_SIZE as u8, num_extensions * BLOCK_SIZE)?
+                    match num_extensions {
+                        0 => vec![],
+                        _ => read(BLOCK_SIZE as u8, num_extensions * BLOCK_SIZE)?,
+                    }
                 }
-                // Something else, obviously broken
+                // Something else, probably broken
                 _ => vec![],
             };
+            data_extensions.chunks_exact(BLOCK_SIZE).for_each(print_checksum);
+
             // Return complete byte stream
             Ok([data_base, data_extensions].concat())
         }
+
         // Explicitly read as many blocks as specified by user
-        Some(blocks) => read(0x00, blocks * BLOCK_SIZE),
+        Some(blocks) => {
+            // Read blocks
+            let data = read(0x00, blocks * BLOCK_SIZE)?;
+            data.chunks_exact(BLOCK_SIZE).for_each(print_checksum);
+
+            // Return complete byte stream
+            Ok(data)
+        }
     }
 }

src/lib.rs

@@ -1,4 +1,5 @@
 pub mod args;
+pub mod checksum;
 pub mod i2c;
-pub mod misc;
+pub mod io;
 pub mod std;

src/std.rs

@@ -1,6 +1,6 @@
 use std::io::{self, Read, Write};
 
-pub fn read_from_std(data_length: usize) -> Result<Vec<u8>, std::io::Error> {
+pub fn read_from_stdin(data_length: usize) -> Result<Vec<u8>, std::io::Error> {
     // Buffer to read into
     let mut data = vec![0; data_length];
     // Read from stdin
@@ -8,8 +8,8 @@ pub fn read_from_std(data_length: usize) -> Result<Vec<u8>, std::io::Error> {
     Ok(data)
 }
 
-pub fn write_to_std(data: &[u8]) -> Result<(), std::io::Error> {
+pub fn write_to_stdout(data: &[u8]) -> Result<(), std::io::Error> {
     // Write data to stdout
     let mut stdout = io::stdout().lock();
-    stdout.write_all(&data)
+    stdout.write_all(data)
 }