Conventions used

There are a number of text conventions used throughout this book.

Code in text: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "The parent IRQ is not requested here using any of the request_irq() family methods because gpiochip_set_chained_irqchip() will invoke irq_set_chained_handler_and_data() under the hood."

A block of code is set as follows:

static int fake_probe(struct i2c_client *client,                       const struct i2c_device_id *id)
{
    [...]
    mutex_init(&data->mutex);
    [...]
}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

static int __init my_init(void)
{
    pr_info('Wait queue example\n');
    INIT_WORK(&wrk, work_handler);
    schedule_work(&wrk);
    pr_info('Going to sleep %s\n', __FUNCTION__);
    wait_event_interruptible(my_wq, condition != 0);
    pr_info('woken up by the work job\n');
    return 0;}

Any command-line input or output is written as follows:

# echo 1 >/sys/module/printk/parameters/time
# cat /sys/module/printk/parameters/time

Bold: Indicates a new term, an important word, or words that you see onscreen. Here is an example: "The simple-mfd helper was introduced to handle zero conf/hacks subdevice registering, and syscon was introduced for sharing a device's memory region with other devices."

Tips or important notes

Appear like this.