What does a controller do?
If you have ever used a computer, you have interacted with an operating system (OS). An OS is a software that manages the hardware and software resources of a computer, such as the CPU, memory, disk, network, and peripherals. But how does the OS communicate with these devices? The answer is through controllers. In this article, you will learn what a controller is, what types of controllers exist, and how they work.
A device controller is a hardware component that controls a specific type of device, such as a disk drive, a keyboard, or a printer. A device controller has a set of registers that store data and commands, and a logic circuit that performs the operations. A device controller can also generate interrupts to notify the OS of the completion or failure of an operation.
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As funções de um controlador de dispositivo incluem a comunicação com o dispositivo de hardware, a tradução de comandos de alto nível do sistema operativo em comandos de baixo nível que o dispositivo possa compreender, a gestão do fluxo de dados entre o dispositivo e o sistema operativo e o fornecimento de uma interface de software para o sistema operativo interagir com o dispositivo.
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Os dispositivos contam com controladores encarregados de coordenar as instruções do usuário no sistema operacional. Nesse contexto, os controladores são componentes de hardware responsáveis por orientar o desempenho da memória e outros elementos, assegurando a execução eficiente das atividades principais.
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The term "controller" in operating systems generally refers to a component that oversees and manages specific aspects of a computer system, such as storage, input/output operations, memory, or graphics. The exact role and responsibilities of a controller depend on its specific type and the hardware it is associated with.
A controller driver is a software component that interacts with a device controller. A controller driver knows how to read and write the registers of the controller, and how to handle the interrupts. A controller driver is usually part of the OS kernel, and provides a uniform interface for the OS to access different types of devices.
A device file is a special file that represents a device in the OS. A device file has a name, permissions, and a device number that identifies the device controller and the device unit. For example, /dev/sda is a device file that represents the first disk drive in Linux. A device file allows the OS and the user programs to use the standard file operations, such as open, read, write, and close, to access the device.
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As funções de um arquivo de dispositivo incluem a comunicação com o dispositivo de hardware, a tradução de comandos de alto nível do sistema operativo em comandos de baixo nível que o dispositivo possa compreender, a gestão do fluxo de dados entre o dispositivo e o sistema operativo e o fornecimento de uma interface de software para o sistema operativo interagir com o dispositivo.
I/O scheduling is the process of deciding the order and timing of the I/O requests sent to a device controller. I/O scheduling aims to optimize the performance and efficiency of the I/O system, by reducing the waiting time, maximizing the throughput, and balancing the load. I/O scheduling can be done by the OS, the controller driver, or the device controller itself, depending on the level of intelligence and autonomy of the controller.
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As requests são atendidas pelo sistema operacional usando três segmentos simples. Controlador de tráfego de E / S: mantém o controle do status de todos os dispositivos, unidades de controle e canais de comunicação. Agendador de E / S: executa as políticas usadas pelo sistema operacional para alocar e acessar o dispositivo, unidades de controle e canais de comunicação. Manipulador de dispositivo de E / S: Atende às interrupções do dispositivo e lidera a transferência de dados.
DMA (Direct Memory Access) is a technique that allows a device controller to transfer data directly to or from the main memory, without involving the CPU. DMA reduces the CPU overhead and improves the I/O speed. DMA requires a DMA controller, which is a special hardware that can access the memory bus and coordinate with the device controller and the CPU. I/O channels are extensions of the DMA concept, which provide more functionality and flexibility for the I/O system. I/O channels are special processors that can execute I/O programs and handle multiple devices and transfers.
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O DMA é uma técnica que permite a transferência direta de dados entre dispositivos de E/S e a memória principal, sem a intervenção da CPU. O canal DMA é um controlador específico que gerencia essas operações de transferência de dados. O DMA é útil para acelerar a transferência de grandes volumes de dados, como quando um dispositivo de armazenamento lê ou grava dados na memória.
I/O virtualization is a technique that allows multiple virtual machines (VMs) to share the same physical I/O devices. I/O virtualization requires a hypervisor, which is a software that manages the VMs and their resources. The hypervisor can either emulate the device controllers for each VM, or use hardware-assisted methods to partition and assign the device controllers to different VMs. I/O virtualization improves the resource utilization and scalability of the I/O system.
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