= GIET_VM / Peripherals Drivers =

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The GIET_VM supports two types of peripheral components: '''External peripherals''' are located in one single cluster (called ''cluster_io'', and identified by the ''X_IO,Y_IO'' variables). '''Internal peripherals''' (such as DMA, XCU, or MMC) are replicated in all clusters.

Each driver xxx_driver define two low-level functions ''_xxx_get_register()'' and ''_xxx_set_register()''
to access the peripheral addressable registers. These functions are in charge to compute the peripheral registers addresses, taking into account the peripheral base address, the register index, and the cluster coordinates: 

 * '''External peripherals''': All accesses use virtual addresses if the MMU (Memory management Unit) is activated, or physical addresses if it is not. In this case, the physical address is computed as pbase = SEG_XXX_BASE + cluster_io << 32.

 * '''Internal peripherals''': All accesses use virtual addresses, and the MMU must be activated. The peripheral virtual base address is computed as vbase = SEG_XXX_BASE + cluster_xy * PERI_CLUSTER_INCREMENT. 

The X_IO, Y_IO, and PERI_CLUSTER_INCREMENT variables must be defined in the ''hard_config.h" file.

Some peripherals (TTY, TIM, NIC, CMA, HBA) are multi-channels peripherals: Each channel provide an independent set of addressable registers, and each channel can be seen as an independent hardware resource. For  multi-channels peripherals, the GIET_VM allows an user application to allocate a ''private'' peripheral channel, that cannot be used by other applications.  The corresponding channel index is stored in the calling task context. For some peripherals (such as TTY or TIM), the allocated channel can be shared by all tasks in the same vspace as the calling task.

 === [wiki:bdv_driver     BDV  (Block Device controller)]
 
 === [wiki:cma_driver     CMA (Chained Buffer DMA controller)]

 === [wiki:dma_driver     DMA (Multi-Channels DMA controller)]

 === [wiki:hba_driver     HBA (AHCI Disk controller)]

 === [wiki:iob_driver     IOB (I/O Bridge controller)]

 === [wiki:ioc_driver     IOC (Generic I/O controller)]

 === [wiki:mmc_driver     MMC (Memory Cache controller)]

 === [wiki:mwr_driver     MWR (MWMR_DMA controller)]

 === [wiki:nic_driver     NIC (Gigabit Ethernet Network controller)]

 === [wiki:pic_driver     PIC (External Peripherals Interrupt controller)]

 === [wiki:rdk_driver     RDK (RamDisk)]

 === [wiki:sim_driver     SIM (Monitor controller)]

 === [wiki:sdc_driver     SDC (SDC Disk controller)]

 === [wiki:tim_driver     TIM (Multi Timers controller)]

 === [wiki:tty_driver     TTY (Multi Terminals TTY controller)]

 === [wiki:xcu_driver     XCU (Extended Interrupt controller)]