Console Subsystem

The Console Subsystem is made up of

• the console drivers, providing console devices

• the implementation of the subsystem itself, providing means for managing consoles

The Console Subsystem is implemented in os/drivers/console/console.c.

This simple subsystem allocates new consoles and provides a generic open function that dispatches to the respective console. It furthermore provides a means to set and get the initial (boot) console.

Initialization

This subsystem is initialized by calling

void console_init(void)

Initialize the console subsystem.

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Allocating a Console

A new console is allocated by calling

console_t *console_alloc(void)

Allocate, initialize and return a new console.

Console operations (console_t::con_ops) need to be provided by the actual console implementation.

Note

This function is intended to be called from the respective console driver.

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Datatypes Provided by the Subsystem

Console Data Structure

The data structure keeping track of console-related data

struct console_t

Console state and operations (backend and frontend).

Tracks the state, e.g., cursor x and y position, and stores the operations provided of and required for a (virtual) console. These operations (con_ops) will be implemented by a console driver and provided to higher-level system components.

Public Members

const console_operations_tconsole_operations_t *con_ops

The operations provided by a console frontend.

unsigned int pos_x

The column for new strings to be printed.

unsigned int pos_y

The row for new strings to be printed.

unsigned int width

The number of columns the backend provides.

unsigned int height

The number of rows the backend provides.

uint8_t default_attribute

The default attribute to use for characters.

void *driver_data

Driver-specific private data.

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Console Operations

The interface between higher-level system components and the console frontend.

struct console_operations_t

Callbacks provided by console drivers to higher-level components.

These callbacks provide other parts of the system with means of, e.g., writing text to a console. The callbacks have to be implemented by the respective console frontend. They can be used, for instance, in printk to output text to the screen.

This data structure and the callbacks defined in it are based on struct console from the Linux kernel (as of 6.17.5). They are adapted and simplified and may long have diverged in order to make tomOSii a prototypical teaching operating system.

Public Members

int (*open)(console_t *console)

Open console console.

void (*write)(console_t *console, const char *string, unsigned int count)

Write count characters from string to console.

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