Now a brief review of the functions. This discussion will use generic -names for the functions — your driver should use hardware-specific -names to maintain uniqueness against any other drivers.
static bool DRV_HDWR_init(struct cyg_netdevtab_entry *tab) |
struct eth_drv_sc *sc = (struct eth_drv_sc *)tab->device_instance; - ....initialization code.... - // Initialize upper level driver - (sc->funs->eth_drv->init)( sc, unsigned char *enaddr ); |
Note: The ethernet station address -(ESA) -is supposed to be a -world-unique, 48 bit address for this particular ethernet interface. -Typically it is provided by the board/hardware manufacturer in ROM.
In many packages it is possible for the -ESA -to be set from RedBoot, -(perhaps from 'fconfig' data), hard-coded from -CDL, or from an EPROM. -A driver should choose a run-time specified -ESA -(e.g. from RedBoot) -preferentially, otherwise (in order) it should use a CDL specified -ESA -if one has been set, otherwise an EPROM set -ESA, or otherwise -fail. See the cl/cs8900a -ethernet driver for an example.
static void -HRDWR_start(struct eth_drv_sc *sc, unsigned char *enaddr, int flags) |
Note: This function will be called whenever the -up/down state of the logical interface changes, e.g. when the IP address -changes, or when promiscuous mode is selected by means of an -ioctl() call in the application. -This may occur more than once, so this function needs to -be prepared for that case.
Note: In future, the flags -field (currently unused) may be used to tell the -function how to start up, e.g. whether interrupts will be used, -alternate means of selecting promiscuous mode etc.
static void HRDWR_stop(struct eth_drv_sc *sc) |
static int -HRDWR_control( - struct eth_drv_sc *sc, unsigned long key, - void *data, int len) |
The key parameter selects the operation, and the -data and len params point describe, -as required, some data for the operation in question.
Available Operations:
This operation sets the ethernet station address (ESA or MAC) for the -device. Normally this address is kept in non-volatile memory and is -unique in the world. This function must at least set the interface to -use the new address. It may also update the NVM as appropriate.
These acquire a set of statistical counters from the interface, and write -the information into the memory pointed to by data. -The “UD” variant explicitly instructs the driver to acquire -up-to-date values. This is a separate option because doing so may take -some time, depending on the hardware.
The definition of the data structure is in -cyg/io/eth/eth_drv_stats.h.
This call is typically made by SNMP, see Chapter 47.
This entry instructs the device to set up multicast packet filtering -to receive only packets addressed to the multicast ESAs in the list pointed -to by data.
The format of the data is a 32-bit count of the ESAs in the list, followed -by packed bytes which are the ESAs themselves, thus: -
#define ETH_DRV_MAX_MC 8
-struct eth_drv_mc_list {
- int len;
- unsigned char addrs[ETH_DRV_MAX_MC][ETHER_ADDR_LEN];
-}; |
This entry instructs the device to receive all multicast packets, and -delete any explicit filtering which had been set up.
This function should return zero if the specified operation was -completed successfully. It should return non-zero if the operation -could not be performed, for any reason.
static int HRDWR_can_send(struct eth_drv_sc *sc) |
Return the number of packets which could be accepted at this time, zero -implies that the interface is saturated/busy.
struct eth_drv_sg {
- CYG_ADDRESS buf;
- CYG_ADDRWORD len;
-};
-
-static void
-HRDWR_send(
- struct eth_drv_sc *sc,
- struct eth_drv_sg *sg_list, int sg_len,
- int total_len, unsigned long key) |
Note: All data in/out of the driver is specified via a -“scatter-gather” -list. This is just an array of address/length pairs which describe -sections of data to move (in the order given by the array), as in the -struct eth_drv_sg defined above and pointed to by -sg_list.
Once the data has been successfully sent by the interface (or if an -error occurs), the driver should call -(sc->funs->eth_drv->tx_done)() -(see the Section called Callback Tx-Done function) -using the specified key. -Only then will the upper layers release the resources -for that packet and start another transmission.
Note: In future, this function may be extended so that the data need not be -copied by having the function return a “disposition” code -(done, send pending, etc). At this point, you should move the data to some -“safe” location before returning.
static void -HRDWR_deliver(struct eth_drv_sc *sc) |
After handling any outstanding incoming packets or pending transmission -status, it can unmask the device's interrupts, and free any relevant -resources so it can process further packets.
It will be called when the interrupt handler for the network device -has called -
eth_drv_dsr( vector, count, (cyg_addrword_t)sc ); |
The reason for this slightly convoluted train of events is to keep the DSR -(and ISR) execution time as short as possible, so that other activities of -higher priority than network servicing are not denied the CPU by network -traffic.
To deliver a newly-received packet into the network stack, the deliver -routine must call -
(sc->funs->eth_drv->recv)(sc, len); |
static void -HRDWR_recv( - struct eth_drv_sc *sc, - struct eth_drv_sg *sg_list, int sg_len) |
(sc->funs->eth_drv->recv)(struct eth_drv_sc *sc, int total_len) |
A scatter-gather list (struct eth_drv_sg) is used once more, -just like in the send case.
static void -HRDWR_poll(struct eth_drv_sc *sc) |
It is perfectly correct and acceptable for the poll function to look like -this: -
static void
-HRDWR_poll(struct eth_drv_sc *sc)
-{
- my_interrupt_ISR(sc);
- HRDWR_deliver(struct eth_drv_sc *sc);
-} |
static int -HRDWR_int_vector(struct eth_drv_sc *sc) |