= 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 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.

== Shared and private peripherals ==

Some peripherals (such as BDV, SDC, FBF) deliver an unique service, and are shared by all applications under the
kernel supervision.

Some peripherals (TTY, TIM, NIC, CMA) 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 dynamically allocate a ''private'' peripheral channel, that cannot be used by other applications.  The corresponding channel index is stored in the calling thread context. 

 * For TIM, the private timer index is hidden, and can only be used by the thread making the allocation.
 * For TTY, the private channel index is hidden, but the the thread making the allocation can ask a totally private terminal, or a partially shared terminal usable by all threads in the same vspace.
 * For NIC, the channel index is returned to the thread making allocation, and can be used by all threads in the same vspace.  

 === [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:mnc_driver     MNC (Master Network Controller)]

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

 === [wiki:nic_driver     NIC (Multi 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)]