Add code comment to clarify the reason we set ICS with ICR:
the reason was previously undocumented and git
log confused rather than clarified the comments.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
val |= E1000_ICR_INT_ASSERTED;
}
s->mac_reg[ICR] = val;
+
+ /*
+ * Make sure ICR and ICS registers have the same value.
+ * The spec says that the ICS register is write-only. However in practice,
+ * on real hardware ICS is readable, and for reads it has the same value as
+ * ICR (except that ICS does not have the clear on read behaviour of ICR).
+ *
+ * The VxWorks PRO/1000 driver uses this behaviour.
+ */
s->mac_reg[ICS] = val;
+
qemu_set_irq(s->dev.irq[0], (s->mac_reg[IMS] & s->mac_reg[ICR]) != 0);
}