drivers/input/misc/ibm-panel.c

Source file repositories/reference/linux-study-clean/drivers/input/misc/ibm-panel.c

File Facts

System
Linux kernel
Corpus path
drivers/input/misc/ibm-panel.c
Extension
.c
Size
4522 bytes
Lines
197
Domain
Driver Families
Bucket
drivers/input
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct ibm_panel {
	u8 idx;
	u8 command[11];
	u32 keycodes[PANEL_KEYCODES_COUNT];
	spinlock_t lock;	/* protects writes to idx and command */
	struct input_dev *input;
};

static u8 ibm_panel_calculate_checksum(struct ibm_panel *panel)
{
	u8 chksum;
	u16 sum = 0;
	unsigned int i;

	for (i = 0; i < sizeof(panel->command) - 1; ++i) {
		sum += panel->command[i];
		if (sum & 0xff00) {
			sum &= 0xff;
			sum++;
		}
	}

	chksum = sum & 0xff;
	chksum = ~chksum;
	chksum++;

	return chksum;
}

static void ibm_panel_process_command(struct ibm_panel *panel)
{
	u8 button;
	u8 chksum;

	if (panel->command[0] != 0xff && panel->command[1] != 0xf0) {
		dev_dbg(&panel->input->dev, "command invalid: %02x %02x\n",
			panel->command[0], panel->command[1]);
		return;
	}

	chksum = ibm_panel_calculate_checksum(panel);
	if (chksum != panel->command[sizeof(panel->command) - 1]) {
		dev_dbg(&panel->input->dev,
			"command failed checksum: %u != %u\n", chksum,
			panel->command[sizeof(panel->command) - 1]);
		return;
	}

	button = panel->command[2] & 0xf;
	if (button < PANEL_KEYCODES_COUNT) {
		input_report_key(panel->input, panel->keycodes[button],
				 !(panel->command[2] & 0x80));
		input_sync(panel->input);
	} else {
		dev_dbg(&panel->input->dev, "unknown button %u\n",
			button);
	}
}

static int ibm_panel_i2c_slave_cb(struct i2c_client *client,
				  enum i2c_slave_event event, u8 *val)
{
	struct ibm_panel *panel = i2c_get_clientdata(client);

	dev_dbg(&panel->input->dev, "event: %u data: %02x\n", event, *val);

	guard(spinlock_irqsave)(&panel->lock);

	switch (event) {
	case I2C_SLAVE_STOP:
		if (panel->idx == sizeof(panel->command))
			ibm_panel_process_command(panel);
		else
			dev_dbg(&panel->input->dev,
				"command incorrect size %u\n", panel->idx);
		fallthrough;
	case I2C_SLAVE_WRITE_REQUESTED:
		panel->idx = 0;
		break;
	case I2C_SLAVE_WRITE_RECEIVED:
		if (panel->idx < sizeof(panel->command))
			panel->command[panel->idx++] = *val;
		else
			/*
			 * The command is too long and therefore invalid, so set the index
			 * to it's largest possible value. When a STOP is finally received,
			 * the command will be rejected upon processing.
			 */
			panel->idx = U8_MAX;
		break;

Annotation

Implementation Notes