usbs_eth.h

eCos操作系统源码

//  2) the usual ethernet header with a six-byte source MAC
//     address, a six-byte destination MAC address, and a
//     two-byte protocol or length field, for a total header
//     size of 14 bytes.
//  3) an extra two bytes of size info.
//
// For a total of 1516 bytes.
#define CYGNUM_USBS_ETH_MAX_FRAME_SIZE 1514
#define CYGNUM_USBS_ETH_MAXTU (CYGNUM_USBS_ETH_MAX_FRAME_SIZE + 2)
    
// Although the minimum ethernet frame size is 60 bytes, this includes
// padding which is not needed when transferring over USB. Hence the
// actual minimum is just the 14 byte ethernet header plus two bytes
// for the length.
#define CYGNUM_USBS_ETH_MIN_FRAME_SIZE 14
#define CYGNUM_USBS_ETH_MINTU (CYGNUM_USBS_ETH_MIN_FRAME_SIZE + 2)

// Typical USB devices involve DMA operations and hence confusion
// between cached and uncached memory. To make life easier for
// the underlying USB device drivers, this package ensures that
// receive operations always involve buffers that are aligned to
// a cache-line boundary and that are a multiple of the cacheline
// size.
#ifndef HAL_DCACHE_LINE_SIZE
# define CYGNUM_USBS_ETH_RXBUFSIZE      CYGNUM_USBS_ETH_MAXTU
# define CYGNUM_USBS_ETH_RXSIZE         CYGNUM_USBS_ETH_MAXTU    
#else
# define CYGNUM_USBS_ETH_RXBUFSIZE      ((CYGNUM_USBS_ETH_MAXTU + HAL_DCACHE_LINE_SIZE + HAL_DCACHE_LINE_SIZE - 1) \
                                         & ~(HAL_DCACHE_LINE_SIZE - 1))
# define CYGNUM_USBS_ETH_RXSIZE         ((CYGNUM_USBS_ETH_MAXTU + HAL_DCACHE_LINE_SIZE - 1) & ~(HAL_DCACHE_LINE_SIZE - 1))
#endif    
    
// ----------------------------------------------------------------------------
// This data structure serves two purposes. First, it keeps track of
// the information needed by the low-level USB ethernet code, for
// example which endpoints should be used for incoming and outgoing
// packets. Second, if the support for the TCP/IP stack is enabled
// then there are additional fields to support that (e.g. for keeping
// track of statistics).
//
// Arguably the two uses should be separated into distinct data
// structures. That would make it possible to instantiate multiple
// low-level USB-ethernet devices but only have a network driver for
// one of them. Achieving that flexibility would require some extra
// indirection, affecting performance and code-size, and it is not
// clear that that flexibility would ever prove useful. For now having
// a single data structure seems more appropriate.

typedef struct usbs_eth {

    // What endpoints should be used for communication?
    usbs_control_endpoint*      control_endpoint;
    usbs_rx_endpoint*           rx_endpoint;
    usbs_tx_endpoint*           tx_endpoint;
    
    // Is the host ready to receive packets? This state is determined
    // largely by control packets sent from the host. It can change at
    // DSR level.
    volatile cyg_bool   host_up;

    // Has the host-side set promiscuous mode? This is relevant to the
    // network driver which may need to do filtering based on the MAC
    // address and host-side promiscuity.
    volatile cyg_bool   host_promiscuous;

    // The host MAC address. This is the address supplied to the
    // host's TCP/IP stack and filled in by the init function. There
    // is no real hardware to extract the address from.
    unsigned char       host_MAC[6];

    // Needed for callback operations.
    void                (*tx_callback_fn)(struct usbs_eth*, void*, int);
    void*               tx_callback_arg;

    void                (*rx_callback_fn)(struct usbs_eth*, void*, int);
    void*               rx_callback_arg;

    // RX operations just block if the host is not connected, resuming
    // when a connection is established. This means saving the buffer
    // pointer so that when the host comes back up the rx operation
    // proper can start. This is not quite consistent because if the
    // connection breaks while an RX is in progress there will be a
    // callback with an error code whereas an RX on a broken
    // connection just blocks, but this does fit neatly into an
    // event-driven I/O model.
    unsigned char*      rx_pending_buf;
    
#ifdef CYGPKG_USBS_ETHDRV
    // Has the TCP/IP stack brought up this interface yet?
    cyg_bool            ecos_up;

    // Is there an ongoing receive? Cancelling a receive operation
    // during a stop() may be difficult, and a stop() may be followed
    // immediately by a restart.
    cyg_bool            rx_active;
    
    // The eCos-side MAC. If the host and the eCos stack are to
    // communicate then they must be able to address each other, i.e.
    // they need separate addresses. Again there is no real hardware
    // to extract the address from so it has to be supplied by higher
    // level code via e.g. an ioctl().
    unsigned char       ecos_MAC[6];
    
    // SNMP statistics
# ifdef CYGFUN_USBS_ETHDRV_STATISTICS
    unsigned int        interrupts;
    unsigned int        tx_count;
    unsigned int        rx_count;
    unsigned int        rx_short_frames;
    unsigned int        rx_too_long_frames;
# endif
    
    // The need for a receive buffer is unavoidable for now because
    // the network driver interface does not support pre-allocating an
    // mbuf and then passing it back to the stack later. Ideally the
    // rx operation would read a single USB packet, determine the
    // required mbuf size from the 2-byte header, copy the initial
    // data, and then read more USB packets. Alternatively, a
    // 1516 byte mbuf could be pre-allocated and then the whole
    // transfer could go there, potentially wasting some mbuf space.
    // None of this is possible at present.
    //
    // Also, typically there will be complications because of
    // dependencies on DMA, cached vs. uncached memory, etc.
    unsigned char       rx_buffer[CYGNUM_USBS_ETH_RXBUFSIZE];
    unsigned char*      rx_bufptr;
    cyg_bool            rx_buffer_full;

    // It should be possible to eliminate the tx buffer. The problem
    // is that the protocol requires 2 bytes to be prepended, and that
    // may not be possible with the buffer supplied by higher-level
    // code. Eliminating this buffer would either require USB
    // device drivers to implement gather functionality on transmits,
    // or it would impose a dependency on higher-level code.
    unsigned char       tx_buffer[CYGNUM_USBS_ETH_MAXTU];
    cyg_bool            tx_buffer_full;
    cyg_bool            tx_done;
    unsigned long       tx_key;
    
    // Prevent recursion send()->tx_done()->can_send()/send()
    cyg_bool            tx_in_send;
#endif
    
} usbs_eth;

// The package automatically instantiates one USB ethernet device.
extern usbs_eth usbs_eth0;

// ----------------------------------------------------------------------------
// If the network driver option is enabled then the package also
// provides a single cyg_netdevtab_entry. This is exported so that
// application code can clone the entry.
#ifdef CYGPKG_USBS_ETHDRV
extern cyg_netdevtab_entry_t usbs_eth_netdev0;    
#endif    
    
// ----------------------------------------------------------------------------
// A C interface to the low-level USB code.
    
// Initialize the USBS-eth support for a particular usbs_eth device.
// This associates a usbs_eth structure with specific endpoints.
extern void usbs_eth_init(usbs_eth*, usbs_control_endpoint*, usbs_rx_endpoint*, usbs_tx_endpoint*, unsigned char*);
    
// Start an asynchronous transmit of a single buffer of up to
// CYGNUM_USBS_ETH_MAXTU bytes. This buffer should contain a 2-byte
// size field, a 14-byte ethernet header, and upto 1500 bytes of
// payload. When the transmit has completed the callback function (if
// any) will be invoked with the specified pointer. NOTE: figure out
// what to do about error reporting
extern void usbs_eth_start_tx(usbs_eth*, unsigned char*, void (*)(usbs_eth*, void*, int), void*);

// Start an asynchronous receive of an ethernet packet. The supplied
// buffer should be at least CYGNUM_USBS_ETH_MAXTU bytes. When a
// complete ethernet frame has been received or when some sort of
// error occurs the callback function will be invoked. The third
// argument
extern void usbs_eth_start_rx(usbs_eth*, unsigned char*, void (*)(usbs_eth*, void*, int), void*);

// The handler for application class control messages. The init call
// will install this in the control endpoint by default. However the
// handler is fairly dumb: it assumes that all application control
// messages are for the ethernet interface and does not bother to
// check the control message's destination. This is fine for simple
// USB ethernet devices, but for any kind of multi-function peripheral
// higher-level code will have to perform multiplexing and invoke this
// handler only when appropriate.
extern usbs_control_return usbs_eth_class_control_handler(usbs_control_endpoint*, void*);

// Similarly a handler for state change messages. Installing this
// means that the ethernet code will have sufficient knowledge about
// the state of the USB connection for simple ethernet-only
// peripherals, but not for anything more complicated. In the latter
// case higher-level code will need to keep track of which
// configuration, interfaces, etc. are currently active and explicitly
// enable or disable the ethernet device using the functions below.
extern void usbs_eth_state_change_handler(usbs_control_endpoint*, void*, usbs_state_change, int);
extern void usbs_eth_disable(usbs_eth*);
extern void usbs_eth_enable(usbs_eth*);    
    
#ifdef __cplusplus
} // extern "C"
#endif

#endif // CYGONCE_USBS_ETH_H_