在 2013-02-15五的 20:16 -0800，Simon Glass写道：
> Use the key-matrix layer to interpret key scan information from the EC
> and inject input based on the FDT-supplied key map. This driver registers
> itself with the ChromeOS EC driver to perform communications.
[snip ...]
> +/*
> + * Returns true when there is at least one combination of pressed keys that
> + * results in ghosting.
> + */
> +static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t
> *buf)
> +{
> + int row;
> +
> + /*
> + * Ghosting happens if for any pressed key X there are other keys
> + * pressed both in the same row and column of X as, for instance,
> + * in the following diagram:
> + *
> + * . . Y . g .
> + * . . . . . .
> + * . . . . . .
> + * . . X . Z .
> + *
> + * In this case only X, Y, and Z are pressed, but g appears to be
> + * pressed too (see Wikipedia).
> + *
> + * We can detect ghosting in a single pass (*) over the keyboard state
> + * by maintaining two arrays. pressed_in_row counts how many pressed
> + * keys we have found in a row. row_has_teeth is true if any of the
> + * pressed keys for this row has other pressed keys in its column. If
> + * at any point of the scan we find that a row has multiple pressed
> + * keys, and at least one of them is at the intersection with a column
> + * with multiple pressed keys, we're sure there is ghosting.
> + * Conversely, if there is ghosting, we will detect such situation for
> + * at least one key during the pass.
> + *
> + * (*) This looks linear in the number of keys, but it's not. We can
> + * cheat because the number of rows is small.
> + */
> + for (row = 0; row < ckdev->rows; row++) {
> + if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row))
> + return true;
> + }
> +
> + return false;
> +}
are you sure your EC's firmware did not do ghost-key detection?
or, did you test ghost-key with/without your own ghost-key detection?
as far as I know, ghost-key should be take care either by keyboard
designer or firmware.
> +
> +/*
> + * Compares the new keyboard state to the old one and produces key
> + * press/release events accordingly. The keyboard state is 13 bytes (one
> byte
> + * per column)
> + */
> +static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
> + uint8_t *kb_state, int len)
> +{
> + int col, row;
> + int new_state;
> + int num_cols;
> +
> + num_cols = len;
> +
> + if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
> + /*
> + * Simple-minded solution: ignore this state. The obvious
> + * improvement is to only ignore changes to keys involved in
> + * the ghosting, but process the other changes.
> + */
> + dev_dbg(ckdev->dev, "ghosting found\n");
> + return;
> + }
> +
> + for (col = 0; col < ckdev->cols; col++) {
> + for (row = 0; row < ckdev->rows; row++) {
> + int code = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
> +
> + new_state = kb_state[col] & (1 << row);
> + if (!!new_state != test_bit(code, ckdev->idev->key)) {
> + dev_dbg(ckdev->dev,
> + "changed: [r%d c%d]: byte %02x\n",
> + row, col, new_state);
> +
> + input_report_key(ckdev->idev, code, new_state);
> + }
> + }
> + }
> + input_sync(ckdev->idev);
> +}
> +
> +static int cros_ec_keyb_open(struct input_dev *dev)
> +{
> + struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
> +
> + return blocking_notifier_chain_register(&ckdev->ec->event_notifier,
> + &ckdev->notifier);
> +}
> +
> +static void cros_ec_keyb_close(struct input_dev *dev)
> +{
> + struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
> +
> + blocking_notifier_chain_unregister(&ckdev->ec->event_notifier,
> + &ckdev->notifier);
> +}
> +
> +static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t
> *kb_state)
> +{
> + return ckdev->ec->command_recv(ckdev->ec, EC_CMD_MKBP_STATE,
> + kb_state, ckdev->cols);
> +}
> +
> +static int cros_ec_keyb_work(struct notifier_block *nb,
> + unsigned long state, void *_notify)
> +{
> + int ret;
> + struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb,
> + notifier);
> + uint8_t kb_state[ckdev->cols];
> +
> + ret = cros_ec_keyb_get_state(ckdev, kb_state);
> + if (ret >= 0)
> + cros_ec_keyb_process(ckdev, kb_state, ret);
> +
> + return NOTIFY_DONE;
> +}
> +
> +/* Clear any keys in the buffer */
> +static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
> +{
> + uint8_t old_state[ckdev->cols];
> + uint8_t new_state[ckdev->cols];
> + unsigned long duration;
> + int i, ret;
> +
> + /*
> + * Keep reading until we see that the scan state does not change.
> + * That indicates that we are done.
> + *
> + * Assume that the EC keyscan buffer is at most 32 deep.
> + */
> + duration = jiffies;
> + ret = cros_ec_keyb_get_state(ckdev, new_state);
> + for (i = 1; !ret && i < 32; i++) {
> + memcpy(old_state, new_state, sizeof(old_state));
> + ret = cros_ec_keyb_get_state(ckdev, new_state);
> + if (0 == memcmp(old_state, new_state, sizeof(old_state)))
> + break;
> + }
> + duration = jiffies - duration;
> + dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
> + jiffies_to_usecs(duration));
> +}
> +
> +static int cros_ec_keyb_probe(struct platform_device *pdev)
> +{
> + struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
> + struct device *dev = ec->dev;
> + struct cros_ec_keyb *ckdev = NULL;
> + struct input_dev *idev = NULL;
> + struct device_node *np;
> + int err;
> +
> + np = pdev->dev.of_node;
> + if (!np)
> + return -ENODEV;
> +
> + ckdev = kzalloc(sizeof(*ckdev), GFP_KERNEL);
> + if (!ckdev) {
> + dev_err(dev, "cannot allocate memory for ckdev\n");
> + return -ENOMEM;
> + }
> + err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
> + &ckdev->cols);
> + if (err)
> + goto fail_alloc_dev;
> +
> + idev = input_allocate_device();
> + if (!idev) {
> + err = -ENOMEM;
> + dev_err(dev, "cannot allocate memory for input device\n");
> + goto fail_alloc_dev;
> + }
> +
> + ckdev->ec = ec;
> + ckdev->notifier.notifier_call = cros_ec_keyb_work;
> + ckdev->dev = dev;
> + dev_set_drvdata(&pdev->dev, ckdev);
> +
> + idev->name = ec->get_name(ec);
> + idev->phys = ec->get_phys_name(ec);
> + __set_bit(EV_REP, idev->evbit);
> +
> + idev->id.bustype = BUS_VIRTUAL;
> + idev->id.version = 1;
> + idev->id.product = 0;
> + idev->dev.parent = &pdev->dev;
> + idev->open = cros_ec_keyb_open;
> + idev->close = cros_ec_keyb_close;
> +
> + ckdev->ghost_filter = of_property_read_bool(np,
> + "google,needs-ghost-filter");
> +
> + err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
> + NULL, idev);
> + if (err) {
> + dev_err(dev, "cannot build key matrix\n");
> + goto fail_matrix;
> + }
> +
> + ckdev->row_shift = get_count_order(ckdev->cols);
> +
> + input_set_capability(idev, EV_MSC, MSC_SCAN);
> + input_set_drvdata(idev, ckdev);
> + ckdev->idev = idev;
> + err = input_register_device(ckdev->idev);
> + if (err) {
> + dev_err(dev, "cannot register input device\n");
> + goto fail_register;
> + }
> +
> + return 0;
> +
> +fail_register:
> + kfree(idev->keycode);
> +fail_matrix:
> + input_free_device(idev);
> +fail_alloc_dev:
> + kfree(ckdev);
> + return err;
> +}
> +
> +static int cros_ec_keyb_remove(struct platform_device *pdev)
> +{
> + struct cros_ec_keyb *ckdev = platform_get_drvdata(pdev);
> + struct input_dev *idev = ckdev->idev;
> +
> + input_unregister_device(idev);
> + kfree(ckdev);
> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int cros_ec_keyb_resume(struct device *dev)
> +{
> + struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
> +
> + /*
> + * When the EC is not a wake source, then it could not have caused the
> + * resume, so we clear the EC's key scan buffer. If the EC was a
> + * wake source (e.g. the lid is open and the user might press a key to
> + * wake) then the key scan buffer should be preserved.
> + */
> + if (ckdev->ec->was_wake_device)
> + cros_ec_keyb_clear_keyboard(ckdev);
> +
> + return 0;
> +}
> +
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
> +
> +static struct platform_driver cros_ec_keyb_driver = {
> + .probe = cros_ec_keyb_probe,
> + .remove = cros_ec_keyb_remove,
> + .driver = {
> + .name = "cros-ec-keyb",
> + .pm = &cros_ec_keyb_pm_ops,
> + },
> +};
> +
> +module_platform_driver(cros_ec_keyb_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
> +MODULE_ALIAS("platform:cros-ec-keyb");
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