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Provide method for accessing BARs on endpoint headers
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IsaacWoods committed Oct 17, 2020
1 parent d9cd580 commit aeb1b249cf6e4563b815011f7ed759198b283405
Showing 1 changed file with 59 additions and 0 deletions.
@@ -184,4 +184,63 @@ impl EndpointHeader {
pub fn header(&self) -> PciHeader {
PciHeader(self.0)
}

/// Get the contents of a BAR in a given slot. Empty bars will return `None`.
///
/// ### Note
/// 64-bit memory BARs use two slots, so if one is decoded in e.g. slot #0, this method should not be called
/// for slot #1
pub fn bar(&self, slot: u8, access: &impl ConfigRegionAccess) -> Option<Bar> {
let offset = 0x10 + (slot as u16) * 4;
let bar = unsafe { access.read(self.0, offset) };

/*
* If bit 0 is `0`, the BAR is in memory. If it's `1`, it's in I/O.
*/
if bar.get_bit(0) == false {
let prefetchable = bar.get_bit(3);
let address = bar.get_bits(4..32) << 4;

// TODO: if the bar is 64-bits, do we need to do this on both BARs?
let size = unsafe {
access.write(self.0, offset, 0xffffffff);
let mut readback = access.read(self.0, offset);
access.write(self.0, offset, address);

/*
* If the entire readback value is zero, the BAR is not implemented, so we return `None`.
*/
if readback == 0x0 {
return None;
}

readback.set_bits(0..4, 0);
1 << readback.trailing_zeros()
};

match bar.get_bits(1..3) {
0b00 => Some(Bar::Memory32 { address, size, prefetchable }),
0b10 => {
let address = {
let mut address = address as u64;
// TODO: do we need to mask off the lower bits on this?
address.set_bits(32..64, unsafe { access.read(self.0, offset + 4) } as u64);
address
};
Some(Bar::Memory64 { address, size: size as u64, prefetchable })
}
// TODO: should we bother to return an error here?
_ => panic!("BAR Memory type is reserved!"),
}
} else {
Some(Bar::Io { port: bar.get_bits(2..32) })
}
}
}

#[derive(Clone, Copy, Debug)]
pub enum Bar {
Memory32 { address: u32, size: u32, prefetchable: bool },
Memory64 { address: u64, size: u64, prefetchable: bool },
Io { port: u32 },
}

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