= GIET-VM / NIC Driver = 

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The [source:soft/giet_vm/giet_drivers/nic_driver.c nic_driver.c] and [source:soft/giet_vm/giet_drivers/nic_driver.h nic_driver.h] files define the NIC driver. 

This component is a multi-channels, giga-bit Ethernet network controller. It is an ''external'', non replicated peripheral. The number of NIC_RX channels (packet receive) and the number of NIC_TX channels (packet send)
are defined by the NB_NIC_CHANNELS parameter in the ''hard_config.h'' file.
For a given channel index, the NIC_TX channel, and the NIC_RX channel use the same MAC address.

The SEG_NIC_BASE address must be defined in the hard_config.h file.

The addressable registers map is defined [source:soft/giet_vm/giet_drivers/nic_driver.h here].

== Access Functions ==

 === 1) unsigned int '''_nic_get_channel_register'''( unsigned int channel,  unsigned int index ) ===
This function returns the value contained in a channel register.
 * '''channel''' : channel index
 * '''index''' : register index

 === 2) void '''_nic_set_channel_register'''( unsigned int channel,  unsigned int index,  unsigned int value ) ===
This function writes a new value in a channel register.
 * '''channel''' : channel index
 * '''index''' : register index
 * '''value''' : written value

 === 3) unsigned int '''_nic_get_global_register'''( unsigned int index ) ===
This function returns the value contained in a global register.
 * '''index''' : register index

 === 4) void '''_nic_set_global_register'''( unsigned int index,  unsigned int value ) ===
This function writes a new value in a global register.
 * '''index''' : register index
 * '''value''' : written value

 === 5) int '''_nic_global_init'''( unsigned int channels, unsigned int vis, unsigned int bc_enable, unsigned int bypass_enable ) ===
This function initializes the global registers.
 * '''channels''' : number of active channels 
 * '''vis''' : bit vector(one bit per active channel)
 * '''bc_enable''' : broadcast packets accepted if non zero
 * '''bypass_enable''' : TX -> RX bypass supported if non zero
This function is used only by the boot code, and return always 0.

 === 6) int '''_nic_channel_start'''( unsigned int channel,  unsigned int mac4,  unsigned int mac2 ) ===
This function activates a NIC_TX or NIC_RX channel:
 * '''channel''' : channel index
 * '''is_rx''' : boolean (RX type if non zero).
 * '''mac4''' : 32 LSB bits of the MAC address.
 * '''mac2''' : 16 MSB bits of the MAC address.
It returns always 0.

=== 7) int '''_nic_channel_stop'''( unsigned int channel, unsigned int is_rx ) ===
This function desactivates a NIC_TX or NIC_RX channel.
It returns always 0.

== __ Interrupt Service Routines__ ==

 === 8) void '''_nic_rx_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
This interrupt Service Routine  handles IRQs from a NIC_RX channel.
WARNING : Not fully implemented yet : no IRQ acknowledge...

 === 9) void '''_nic_tx_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
This interrupt Service Routine  handles IRQs from a NIC_TX channel.
WARNING : Not fully implemented yet : no IRQ acknowledge...