//! Read a real PCI function through one DTB-bounded ECAM Device page.

use super::*;
use os_pci_discovery::{ClaimTable, EcamWindow, Error, BUS_BYTES};

pub fn run(boot: &BootData) -> Result<(), &'static str> {
    let blob = unsafe { core::slice::from_raw_parts(boot.dtb_address as *const u8, boot.dtb_size) };
    let host = dtb::discover_pci_ecam(blob).map_err(|_| "k1425-dtb-host")?;
    let window = EcamWindow::new(host.base, host.size, host.first_bus, host.last_bus)
        .map_err(|_| "k1425-ecam-window")?;
    let mut claims = ClaimTable::<1>::new();
    let config = claims.claim(window, 0, 1, 0, 0)
        .map_err(|_| "k1425-config-claim")?;
    if config.physical != host.base + 0x8000 || claims.count() != 1 {
        return Err("k1425-config-address");
    }
    // SAFETY: the DTB host owns this physical ECAM resource. Boot installed
    // exactly this page as Device-nGnRnE before enabling TTBR0. The claim is
    // live and the DWORD is aligned and fully within the host's bus range.
    let identity = unsafe { read_volatile(config.physical as *const u32) };
    let vendor = identity & 0xffff;
    let device = identity >> 16;
    if vendor != 0x1af4 || device == 0 || device == 0xffff {
        return Err("k1425-virtio-rng-identity");
    }

    // This narrower fixture describes only bus zero; it tests the same
    // checked-address function without attempting a second physical read.
    let narrow = EcamWindow::new(host.base, BUS_BYTES, 0, 0)
        .map_err(|_| "k1425-narrow-window")?;
    let before = claims.snapshot();
    if claims.claim(narrow, 255, 0, 0, 0) != Err(Error::BusOutOfRange)
        || claims.snapshot() != before {
        return Err("k1425-outside-bus-accepted");
    }
    claims.release(config).map_err(|_| "k1425-config-release")?;
    if claims.count() != 0 { return Err("k1425-claim-leak"); }
    write_str("TURKOS/OS/K1425-ECAM: BASE=0x"); write_hex(host.base as usize);
    write_str(" SIZE=0x"); write_hex(host.size as usize);
    write_str(" BUS-END=0x"); write_hex(host.last_bus as usize);
    write_str(" CONFIG=0x"); write_hex(config.physical as usize);
    write_str(" ID=0x"); write_hex(identity as usize);
    write_line(" READS=1 OUTSIDE-BUS255=REJECTED CLAIMS=0");
    Ok(())
}