system/dev/bus/virtio/backends/backend.h

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#pragma once

#include <ddk/protocol/pci.h>
#include <ddk/protocol/pci-lib.h>
#include <fbl/mutex.h>
#include <fbl/unique_ptr.h>
#include <virtio/virtio.h>
#include <lib/zx/handle.h>

// Each backend will implement their own method for initialization / binding
// based on their own internal functionality. Since we will have different
// base drivers at a bind level to bind to pci vs mmio, that layer will
// be able to determine what needs to be called and what parameters to pass.
//
// ex: A device bound as a pci device will know to create a PCI backend
// with the protocol and device info parameters.
namespace virtio {

class Backend {
public:
    Backend() {}
    virtual ~Backend() {
        irq_handle_.reset();
    }
    virtual zx_status_t Bind() = 0;
    virtual void Unbind(){};

    // Returns true if the specified feature bit is set
    virtual bool ReadFeature(uint32_t bit) = 0;
    // Does a Driver -> Device acknowledgement of a feature bit
    virtual void SetFeature(uint32_t bit) = 0;
    // Does a FEATURES_OK check
    virtual zx_status_t ConfirmFeatures() = 0;
    // Device lifecycle methods
    virtual void DriverStatusOk() = 0;
    virtual void DriverStatusAck() = 0;
    virtual void DeviceReset() = 0;

    //// Read/Write the device config
    virtual void DeviceConfigRead(uint16_t offset, uint8_t* value) = 0;
    virtual void DeviceConfigRead(uint16_t offset, uint16_t* value) = 0;
    virtual void DeviceConfigRead(uint16_t offset, uint32_t* value) = 0;
    virtual void DeviceConfigRead(uint16_t offset, uint64_t* value) = 0;
    virtual void DeviceConfigWrite(uint16_t offset, uint8_t value) = 0;
    virtual void DeviceConfigWrite(uint16_t offset, uint16_t value) = 0;
    virtual void DeviceConfigWrite(uint16_t offset, uint32_t value) = 0;
    virtual void DeviceConfigWrite(uint16_t offset, uint64_t value) = 0;

    // Ring methods vary based on backend due to config offsets and field sizes.
    virtual uint16_t GetRingSize(uint16_t index) = 0;
    virtual void SetRing(uint16_t index, uint16_t count, zx_paddr_t pa_desc, zx_paddr_t pa_avail,
                         zx_paddr_t pa_used) = 0;
    virtual void RingKick(uint16_t ring_index) = 0;
    // Expected to read the interrupt status out of the config based on the offset/address
    // specified by the isr capability.
    virtual uint32_t IsrStatus() = 0;
    virtual zx_status_t InterruptValid() = 0;
    virtual zx_status_t WaitForInterrupt() = 0;

    DISALLOW_COPY_ASSIGN_AND_MOVE(Backend);

protected:
    // For protecting irq access / status
    zx::handle irq_handle_;
};

} // namespace virtio