Method write_byte_internal

pci/src/configuration.rs:705–721

Writes a byte to `offset`, optionally enforcing read-only bits.

(&mut self, offset: usize, value: u8, apply_writable_mask: bool)

    /// Writes a byte to `offset`, optionally enforcing read-only bits.
    fn write_byte_internal(&mut self, offset: usize, value: u8, apply_writable_mask: bool) {
        let shift = (offset % 4) * 8;
        let reg_idx = offset / 4;

        if let Some(r) = self.registers.get_mut(reg_idx) {
            let writable_mask = if apply_writable_mask {
                self.writable_bits[reg_idx]
            } else {
                0xffff_ffff
            };
            let mask = (0xffu32 << shift) & writable_mask;
            let shifted_value = (u32::from(value) << shift) & writable_mask;
            *r = *r & !mask | shifted_value;
        } else {
            warn!("bad PCI config write offset {offset}");
        }
    }

    /// Adds a region specified by `config`.  Configures the specified BAR(s) to
    /// report this region and size to the guest kernel.  Enforces a few constraints