input: Add support for keyboard matrix decoding from an fdt

Matrix keyboards require a key map to be set up, and must also deal with
key ghosting.

Create a keyboard matrix management implementation which can be leveraged
by various keyboard drivers. This includes code to read the keymap from
the FDT and perform debouncing.

Signed-off-by: Bernie Thompson <bhthompson@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

1 files changed, 208 insertions, 0 deletions

diff --git a/drivers/input/key_matrix.c b/drivers/input/key_matrix.c
new file mode 100644
index 00000000000..84b898ff384
--- /dev/null
+++ b/drivers/input/key_matrix.c
@@ -0,0 +1,208 @@
+/*
+ * Manage Keyboard Matrices
+ *
+ * Copyright (c) 2012 The Chromium OS Authors.
+ * (C) Copyright 2004 DENX Software Engineering, Wolfgang Denk, wd@denx.de
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <fdtdec.h>
+#include <key_matrix.h>
+#include <malloc.h>
+#include <linux/input.h>
+
+/**
+ * Determine if the current keypress configuration can cause key ghosting
+ *
+ * We figure this out by seeing if we have two or more keys in the same
+ * column, as well as two or more keys in the same row.
+ *
+ * @param config	Keyboard matrix config
+ * @param keys		List of keys to check
+ * @param valid		Number of valid keypresses to check
+ * @return 0 if no ghosting is possible, 1 if it is
+ */
+static int has_ghosting(struct key_matrix *config, struct key_matrix_key *keys,
+			int valid)
+{
+	int key_in_same_col = 0, key_in_same_row = 0;
+	int i, j;
+
+	for (i = 0; i < valid; i++) {
+		/*
+		 * Find 2 keys such that one key is in the same row
+		 * and the other is in the same column as the i-th key.
+		 */
+		for (j = i + 1; j < valid; j++) {
+			if (keys[j].col == keys[i].col)
+				key_in_same_col = 1;
+			if (keys[j].row == keys[i].row)
+				key_in_same_row = 1;
+		}
+	}
+
+	if (key_in_same_col && key_in_same_row)
+		return 1;
+	else
+		return 0;
+}
+
+int key_matrix_decode(struct key_matrix *config, struct key_matrix_key keys[],
+		      int num_keys, int keycode[], int max_keycodes)
+{
+	const u8 *keymap;
+	int valid, upto;
+	int pos;
+
+	debug("%s: num_keys = %d\n", __func__, num_keys);
+	keymap = config->plain_keycode;
+	for (valid = upto = 0; upto < num_keys; upto++) {
+		struct key_matrix_key *key = &keys[upto];
+
+		debug("  valid=%d, row=%d, col=%d\n", key->valid, key->row,
+		      key->col);
+		if (!key->valid)
+			continue;
+		pos = key->row * config->num_cols + key->col;
+		if (config->fn_keycode && pos == config->fn_pos)
+			keymap = config->fn_keycode;
+
+		/* Convert the (row, col) values into a keycode */
+		if (valid < max_keycodes)
+			keycode[valid++] = keymap[pos];
+		debug("    keycode=%d\n", keymap[pos]);
+	}
+
+	/* For a ghost key config, ignore the keypresses for this iteration. */
+	if (valid >= 3 && has_ghosting(config, keys, valid)) {
+		valid = 0;
+		debug("    ghosting detected!\n");
+	}
+	debug("  %d valid keycodes found\n", valid);
+
+	return valid;
+}
+
+/**
+ * Create a new keycode map from some provided data
+ *
+ * This decodes a keycode map in the format used by the fdt, which is one
+ * word per entry, with the row, col and keycode encoded in that word.
+ *
+ * We create a (row x col) size byte array with each entry containing the
+ * keycode for that (row, col). We also search for map_keycode and return
+ * its position if found (this is used for finding the Fn key).
+ *
+ * @param config        Key matrix dimensions structure
+ * @param data          Keycode data
+ * @param len           Number of entries in keycode table
+ * @param map_keycode   Key code to find in the map
+ * @param pos           Returns position of map_keycode, if found, else -1
+ * @return map  Pointer to allocated map
+ */
+static uchar *create_keymap(struct key_matrix *config, u32 *data, int len,
+			    int map_keycode, int *pos)
+{
+	uchar *map;
+
+	if (pos)
+		*pos = -1;
+	map = (uchar *)calloc(1, config->key_count);
+	if (!map) {
+		debug("%s: failed to malloc %d bytes\n", __func__,
+			config->key_count);
+		return NULL;
+	}
+
+	for (; len >= sizeof(u32); data++, len -= 4) {
+		u32 tmp = fdt32_to_cpu(*data);
+		int key_code, row, col;
+		int entry;
+
+		row = (tmp >> 24) & 0xff;
+		col = (tmp >> 16) & 0xff;
+		key_code = tmp & 0xffff;
+		entry = row * config->num_cols + col;
+		map[entry] = key_code;
+		if (pos && map_keycode == key_code)
+			*pos = entry;
+	}
+
+	return map;
+}
+
+int key_matrix_decode_fdt(struct key_matrix *config, const void *blob,
+			  int node)
+{
+	const struct fdt_property *prop;
+	int offset;
+
+	/* Check each property name for ones that we understand */
+	for (offset = fdt_first_property_offset(blob, node);
+		      offset > 0;
+		      offset = fdt_next_property_offset(blob, offset)) {
+		const char *name;
+		int len;
+
+		prop = fdt_get_property_by_offset(blob, offset, NULL);
+		name = fdt_string(blob, fdt32_to_cpu(prop->nameoff));
+		len = strlen(name);
+
+		/* Name needs to match "1,<type>keymap" */
+		debug("%s: property '%s'\n", __func__, name);
+		if (strncmp(name, "1,", 2) || len < 8 ||
+		    strcmp(name + len - 6, "keymap"))
+			continue;
+
+		len -= 8;
+		if (len == 0) {
+			config->plain_keycode = create_keymap(config,
+				(u32 *)prop->data, fdt32_to_cpu(prop->len),
+				KEY_FN, &config->fn_pos);
+		} else if (0 == strncmp(name + 2, "fn-", len)) {
+			config->fn_keycode = create_keymap(config,
+				(u32 *)prop->data, fdt32_to_cpu(prop->len),
+				-1, NULL);
+		} else {
+			debug("%s: unrecognised property '%s'\n", __func__,
+			      name);
+		}
+	}
+	debug("%s: Decoded key maps %p, %p from fdt\n", __func__,
+	      config->plain_keycode, config->fn_keycode);
+
+	if (!config->plain_keycode) {
+		debug("%s: cannot find keycode-plain map\n", __func__);
+		return -1;
+	}
+
+	return 0;
+}
+
+int key_matrix_init(struct key_matrix *config, int rows, int cols)
+{
+	memset(config, '\0', sizeof(*config));
+	config->num_rows = rows;
+	config->num_cols = cols;
+	config->key_count = rows * cols;
+	assert(config->key_count > 0);
+
+	return 0;
+}