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Date: Mon, 18 Jan 2016 21:46:45 +0800
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: Tetsuya Mukawa <mukawa@igel.co.jp>
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Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 3/3] virtio: Add a new layer to abstract pci
	access method
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On Mon, Jan 18, 2016 at 06:13:09PM +0900, Tetsuya Mukawa wrote:
> +struct virtio_pci_access_ops {
> +	uint8_t (*legacy_read8)(struct virtio_hw *hw, uint8_t *addr);
> +	uint16_t (*legacy_read16)(struct virtio_hw *hw, uint16_t *addr);
> +	uint32_t (*legacy_read32)(struct virtio_hw *hw, uint32_t *addr);
> +	void (*legacy_write8)(struct virtio_hw *hw,
> +				uint8_t *addr, uint8_t val);
> +	void (*legacy_write16)(struct virtio_hw *hw,
> +				uint16_t *addr, uint16_t val);
> +	void (*legacy_write32)(struct virtio_hw *hw,
> +				uint32_t *addr, uint32_t val);
> +
> +	uint8_t (*modern_read8)(struct virtio_hw *hw, uint8_t *addr);
> +	uint16_t (*modern_read16)(struct virtio_hw *hw, uint16_t *addr);
> +	uint32_t (*modern_read32)(struct virtio_hw *hw, uint32_t *addr);
> +	void (*modern_write8)(struct virtio_hw *hw,
> +				uint8_t *addr, uint8_t val);
> +	void (*modern_write16)(struct virtio_hw *hw,
> +				uint16_t *addr, uint16_t val);
> +	void (*modern_write32)(struct virtio_hw *hw,
> +				uint32_t *addr, uint32_t val);

One thing about abstraction is that you need define one set of operations,
instead of two similar sets. Thus, you need define following operations
only:

  - read8
  - read16
  - read32
  - write8
  - write16
  - write32

And make a proper assignment after the modern/legacy detection.

> +
> +	int (*map_pci_cfg)(struct virtio_hw *hw);
> +	void (*unmap_pci_cfg)(struct virtio_hw *hw);
> +	void *(*get_cfg_addr)(struct virtio_hw *hw,
> +				struct virtio_pci_cap *cap);
> +	int (*read_pci_cfg)(struct virtio_hw *hw,
> +				void *buf, size_t len, off_t offset);

It'd be good if you can post the patches that use above abstract
operations, so that people can tell if they are properly defined.

	--yliu