Autodetect number of blocks to handle

src/args.rs

@@ -1,8 +1,5 @@
 use clap::Parser;
 
-// Size of EDID binary block
-pub const BLOCK_SIZE: usize = 128;
-
 fn hex_address(a: &str) -> Result<u16, std::num::ParseIntError> {
     u16::from_str_radix(a.trim_start_matches("0x"), 16)
 }
@@ -18,7 +15,7 @@ pub struct Args {
     #[arg(short, long, default_value = "0x50", value_parser = hex_address)]
     pub address: u16,
 
-    /// Number of 128-byte blocks to read, defaults to reading the base block.
-    #[arg(short, long, default_value_t = 1)]
-    pub blocks: usize,
+    /// Number of 128-byte blocks to read, defaults to autodetect from data
+    #[arg(short, long, default_value = None)]
+    pub blocks: Option<usize>,
 }

src/bin/edidread.rs

@@ -1,16 +1,18 @@
 use clap::Parser;
 use rwedid::args::*;
 use rwedid::i2c::*;
-use std::io::{self, Write};
+use rwedid::misc::*;
+use rwedid::std::*;
 
 fn main() -> Result<(), std::io::Error> {
     // Parse command line arguments
     let args = Args::parse();
 
     // Read the data from the chip
-    let bytes = read_from_bus(&args.device, args.address, BLOCK_SIZE * args.blocks)?;
+    let bytes = block_by_block_read(args.blocks, |o, l| {
+        read_from_bus(&args.device, args.address, o, l)
+    })?;
 
     // Write binary blob to stdout
-    let mut stdout = io::stdout().lock();
-    stdout.write_all(&bytes)
+    write_to_std(&bytes)
 }

src/bin/edidwrite.rs

@@ -1,18 +1,15 @@
 use clap::Parser;
 use rwedid::args::*;
 use rwedid::i2c::*;
-use std::io::{self, Read};
+use rwedid::misc::*;
+use rwedid::std::*;
 
 fn main() -> Result<(), std::io::Error> {
     // Parse command line arguments
     let args = Args::parse();
 
     // Read binary from stdin
-    let data_length = args.blocks * BLOCK_SIZE;
-    let mut data = vec![0; data_length];
-
-    // Read binary blob from stdin
-    io::stdin().read_exact(data.as_mut_slice())?;
+    let data = block_by_block_read(args.blocks, |_, l| read_from_std(l))?;
 
     // Write the data to the chip
     write_to_bus(&args.device, args.address, data.as_slice())

src/i2c.rs

@@ -7,6 +7,7 @@ use std::time::Duration;
 pub fn read_from_bus(
     i2c_device: &str,
     slave_address: u16,
+    memory_address: u8,
     data_length: usize,
 ) -> Result<Vec<u8>, std::io::Error> {
     let mut data = vec![0; data_length];
@@ -14,7 +15,7 @@ pub fn read_from_bus(
     let mut dev = LinuxI2CDevice::new(i2c_device, slave_address)?;
     let mut msgs = [
         // Address to read from
-        LinuxI2CMessage::write(&[0x00]),
+        LinuxI2CMessage::write(&[memory_address]),
         // Read data into buffer
         LinuxI2CMessage::read(&mut data),
     ];
@@ -34,9 +35,8 @@ pub fn write_to_bus(
 
     // Write 8 bytes at a time
     for (i, chunk) in data.chunks_exact(8).into_iter().enumerate() {
-
         // Memory address
-        let memory_address : u8 = (i as u8) * 8;
+        let memory_address: u8 = (i as u8) * 8;
         let mut msgs = [
             // Address to write to
             LinuxI2CMessage::write(&[memory_address]),
@@ -47,7 +47,7 @@ pub fn write_to_bus(
         dev.transfer(&mut msgs)?;
 
         thread::sleep(Duration::from_millis(20));
-    };
+    }
 
     Ok(())
 }

src/lib.rs

@@ -1,2 +1,4 @@
 pub mod args;
 pub mod i2c;
+pub mod misc;
+pub mod std;

src/misc.rs

@@ -0,0 +1,31 @@
+// Size of EDID binary block
+pub const BLOCK_SIZE: usize = 128;
+
+pub fn block_by_block_read(
+    blocks: Option<usize>,
+    read: impl Fn(u8, usize) -> Result<Vec<u8>, std::io::Error>,
+) -> Result<Vec<u8>, std::io::Error> {
+    match blocks {
+        // Default: autodetect number of extension blocks
+        None => {
+            // Read first block (128 bytes)
+            let data_base = read(0x00, BLOCK_SIZE)?;
+            // Try to read remaining bytes
+            let data_extensions = match data_base.len() {
+                // Proper 128 byte block
+                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)?
+                }
+                // Something else, obviously broken
+                _ => vec![],
+            };
+            // 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),
+    }
+}

src/std.rs

@@ -0,0 +1,15 @@
+use std::io::{self, Read, Write};
+
+pub fn read_from_std(data_length: usize) -> Result<Vec<u8>, std::io::Error> {
+    // Buffer to read into
+    let mut data = vec![0; data_length];
+    // Read from stdin
+    io::stdin().read_exact(data.as_mut_slice())?;
+    Ok(data)
+}
+
+pub fn write_to_std(data: &[u8]) -> Result<(), std::io::Error> {
+    // Write data to stdout
+    let mut stdout = io::stdout().lock();
+    stdout.write_all(&data)
+}