usb: xhci: add USB2 Link power management BESL support
[linux/fpc-iii.git] / drivers / power / olpc_battery.c
blob1ec810ada5edd4cf4c9299016ef5326a35c800f1
1 /*
2 * Battery driver for One Laptop Per Child board.
4 * Copyright © 2006-2010 David Woodhouse <dwmw2@infradead.org>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/types.h>
14 #include <linux/err.h>
15 #include <linux/device.h>
16 #include <linux/platform_device.h>
17 #include <linux/power_supply.h>
18 #include <linux/jiffies.h>
19 #include <linux/sched.h>
20 #include <linux/olpc-ec.h>
21 #include <asm/olpc.h>
24 #define EC_BAT_VOLTAGE 0x10 /* uint16_t, *9.76/32, mV */
25 #define EC_BAT_CURRENT 0x11 /* int16_t, *15.625/120, mA */
26 #define EC_BAT_ACR 0x12 /* int16_t, *6250/15, µAh */
27 #define EC_BAT_TEMP 0x13 /* uint16_t, *100/256, °C */
28 #define EC_AMB_TEMP 0x14 /* uint16_t, *100/256, °C */
29 #define EC_BAT_STATUS 0x15 /* uint8_t, bitmask */
30 #define EC_BAT_SOC 0x16 /* uint8_t, percentage */
31 #define EC_BAT_SERIAL 0x17 /* uint8_t[6] */
32 #define EC_BAT_EEPROM 0x18 /* uint8_t adr as input, uint8_t output */
33 #define EC_BAT_ERRCODE 0x1f /* uint8_t, bitmask */
35 #define BAT_STAT_PRESENT 0x01
36 #define BAT_STAT_FULL 0x02
37 #define BAT_STAT_LOW 0x04
38 #define BAT_STAT_DESTROY 0x08
39 #define BAT_STAT_AC 0x10
40 #define BAT_STAT_CHARGING 0x20
41 #define BAT_STAT_DISCHARGING 0x40
42 #define BAT_STAT_TRICKLE 0x80
44 #define BAT_ERR_INFOFAIL 0x02
45 #define BAT_ERR_OVERVOLTAGE 0x04
46 #define BAT_ERR_OVERTEMP 0x05
47 #define BAT_ERR_GAUGESTOP 0x06
48 #define BAT_ERR_OUT_OF_CONTROL 0x07
49 #define BAT_ERR_ID_FAIL 0x09
50 #define BAT_ERR_ACR_FAIL 0x10
52 #define BAT_ADDR_MFR_TYPE 0x5F
54 /*********************************************************************
55 * Power
56 *********************************************************************/
58 static int olpc_ac_get_prop(struct power_supply *psy,
59 enum power_supply_property psp,
60 union power_supply_propval *val)
62 int ret = 0;
63 uint8_t status;
65 switch (psp) {
66 case POWER_SUPPLY_PROP_ONLINE:
67 ret = olpc_ec_cmd(EC_BAT_STATUS, NULL, 0, &status, 1);
68 if (ret)
69 return ret;
71 val->intval = !!(status & BAT_STAT_AC);
72 break;
73 default:
74 ret = -EINVAL;
75 break;
77 return ret;
80 static enum power_supply_property olpc_ac_props[] = {
81 POWER_SUPPLY_PROP_ONLINE,
84 static struct power_supply olpc_ac = {
85 .name = "olpc-ac",
86 .type = POWER_SUPPLY_TYPE_MAINS,
87 .properties = olpc_ac_props,
88 .num_properties = ARRAY_SIZE(olpc_ac_props),
89 .get_property = olpc_ac_get_prop,
92 static char bat_serial[17]; /* Ick */
94 static int olpc_bat_get_status(union power_supply_propval *val, uint8_t ec_byte)
96 if (olpc_platform_info.ecver > 0x44) {
97 if (ec_byte & (BAT_STAT_CHARGING | BAT_STAT_TRICKLE))
98 val->intval = POWER_SUPPLY_STATUS_CHARGING;
99 else if (ec_byte & BAT_STAT_DISCHARGING)
100 val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
101 else if (ec_byte & BAT_STAT_FULL)
102 val->intval = POWER_SUPPLY_STATUS_FULL;
103 else /* er,... */
104 val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
105 } else {
106 /* Older EC didn't report charge/discharge bits */
107 if (!(ec_byte & BAT_STAT_AC)) /* No AC means discharging */
108 val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
109 else if (ec_byte & BAT_STAT_FULL)
110 val->intval = POWER_SUPPLY_STATUS_FULL;
111 else /* Not _necessarily_ true but EC doesn't tell all yet */
112 val->intval = POWER_SUPPLY_STATUS_CHARGING;
115 return 0;
118 static int olpc_bat_get_health(union power_supply_propval *val)
120 uint8_t ec_byte;
121 int ret;
123 ret = olpc_ec_cmd(EC_BAT_ERRCODE, NULL, 0, &ec_byte, 1);
124 if (ret)
125 return ret;
127 switch (ec_byte) {
128 case 0:
129 val->intval = POWER_SUPPLY_HEALTH_GOOD;
130 break;
132 case BAT_ERR_OVERTEMP:
133 val->intval = POWER_SUPPLY_HEALTH_OVERHEAT;
134 break;
136 case BAT_ERR_OVERVOLTAGE:
137 val->intval = POWER_SUPPLY_HEALTH_OVERVOLTAGE;
138 break;
140 case BAT_ERR_INFOFAIL:
141 case BAT_ERR_OUT_OF_CONTROL:
142 case BAT_ERR_ID_FAIL:
143 case BAT_ERR_ACR_FAIL:
144 val->intval = POWER_SUPPLY_HEALTH_UNSPEC_FAILURE;
145 break;
147 default:
148 /* Eep. We don't know this failure code */
149 ret = -EIO;
152 return ret;
155 static int olpc_bat_get_mfr(union power_supply_propval *val)
157 uint8_t ec_byte;
158 int ret;
160 ec_byte = BAT_ADDR_MFR_TYPE;
161 ret = olpc_ec_cmd(EC_BAT_EEPROM, &ec_byte, 1, &ec_byte, 1);
162 if (ret)
163 return ret;
165 switch (ec_byte >> 4) {
166 case 1:
167 val->strval = "Gold Peak";
168 break;
169 case 2:
170 val->strval = "BYD";
171 break;
172 default:
173 val->strval = "Unknown";
174 break;
177 return ret;
180 static int olpc_bat_get_tech(union power_supply_propval *val)
182 uint8_t ec_byte;
183 int ret;
185 ec_byte = BAT_ADDR_MFR_TYPE;
186 ret = olpc_ec_cmd(EC_BAT_EEPROM, &ec_byte, 1, &ec_byte, 1);
187 if (ret)
188 return ret;
190 switch (ec_byte & 0xf) {
191 case 1:
192 val->intval = POWER_SUPPLY_TECHNOLOGY_NiMH;
193 break;
194 case 2:
195 val->intval = POWER_SUPPLY_TECHNOLOGY_LiFe;
196 break;
197 default:
198 val->intval = POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
199 break;
202 return ret;
205 static int olpc_bat_get_charge_full_design(union power_supply_propval *val)
207 uint8_t ec_byte;
208 union power_supply_propval tech;
209 int ret, mfr;
211 ret = olpc_bat_get_tech(&tech);
212 if (ret)
213 return ret;
215 ec_byte = BAT_ADDR_MFR_TYPE;
216 ret = olpc_ec_cmd(EC_BAT_EEPROM, &ec_byte, 1, &ec_byte, 1);
217 if (ret)
218 return ret;
220 mfr = ec_byte >> 4;
222 switch (tech.intval) {
223 case POWER_SUPPLY_TECHNOLOGY_NiMH:
224 switch (mfr) {
225 case 1: /* Gold Peak */
226 val->intval = 3000000*.8;
227 break;
228 default:
229 return -EIO;
231 break;
233 case POWER_SUPPLY_TECHNOLOGY_LiFe:
234 switch (mfr) {
235 case 1: /* Gold Peak, fall through */
236 case 2: /* BYD */
237 val->intval = 2800000;
238 break;
239 default:
240 return -EIO;
242 break;
244 default:
245 return -EIO;
248 return ret;
251 static int olpc_bat_get_charge_now(union power_supply_propval *val)
253 uint8_t soc;
254 union power_supply_propval full;
255 int ret;
257 ret = olpc_ec_cmd(EC_BAT_SOC, NULL, 0, &soc, 1);
258 if (ret)
259 return ret;
261 ret = olpc_bat_get_charge_full_design(&full);
262 if (ret)
263 return ret;
265 val->intval = soc * (full.intval / 100);
266 return 0;
269 static int olpc_bat_get_voltage_max_design(union power_supply_propval *val)
271 uint8_t ec_byte;
272 union power_supply_propval tech;
273 int mfr;
274 int ret;
276 ret = olpc_bat_get_tech(&tech);
277 if (ret)
278 return ret;
280 ec_byte = BAT_ADDR_MFR_TYPE;
281 ret = olpc_ec_cmd(EC_BAT_EEPROM, &ec_byte, 1, &ec_byte, 1);
282 if (ret)
283 return ret;
285 mfr = ec_byte >> 4;
287 switch (tech.intval) {
288 case POWER_SUPPLY_TECHNOLOGY_NiMH:
289 switch (mfr) {
290 case 1: /* Gold Peak */
291 val->intval = 6000000;
292 break;
293 default:
294 return -EIO;
296 break;
298 case POWER_SUPPLY_TECHNOLOGY_LiFe:
299 switch (mfr) {
300 case 1: /* Gold Peak */
301 val->intval = 6400000;
302 break;
303 case 2: /* BYD */
304 val->intval = 6500000;
305 break;
306 default:
307 return -EIO;
309 break;
311 default:
312 return -EIO;
315 return ret;
318 /*********************************************************************
319 * Battery properties
320 *********************************************************************/
321 static int olpc_bat_get_property(struct power_supply *psy,
322 enum power_supply_property psp,
323 union power_supply_propval *val)
325 int ret = 0;
326 __be16 ec_word;
327 uint8_t ec_byte;
328 __be64 ser_buf;
330 ret = olpc_ec_cmd(EC_BAT_STATUS, NULL, 0, &ec_byte, 1);
331 if (ret)
332 return ret;
334 /* Theoretically there's a race here -- the battery could be
335 removed immediately after we check whether it's present, and
336 then we query for some other property of the now-absent battery.
337 It doesn't matter though -- the EC will return the last-known
338 information, and it's as if we just ran that _little_ bit faster
339 and managed to read it out before the battery went away. */
340 if (!(ec_byte & (BAT_STAT_PRESENT | BAT_STAT_TRICKLE)) &&
341 psp != POWER_SUPPLY_PROP_PRESENT)
342 return -ENODEV;
344 switch (psp) {
345 case POWER_SUPPLY_PROP_STATUS:
346 ret = olpc_bat_get_status(val, ec_byte);
347 if (ret)
348 return ret;
349 break;
350 case POWER_SUPPLY_PROP_CHARGE_TYPE:
351 if (ec_byte & BAT_STAT_TRICKLE)
352 val->intval = POWER_SUPPLY_CHARGE_TYPE_TRICKLE;
353 else if (ec_byte & BAT_STAT_CHARGING)
354 val->intval = POWER_SUPPLY_CHARGE_TYPE_FAST;
355 else
356 val->intval = POWER_SUPPLY_CHARGE_TYPE_NONE;
357 break;
358 case POWER_SUPPLY_PROP_PRESENT:
359 val->intval = !!(ec_byte & (BAT_STAT_PRESENT |
360 BAT_STAT_TRICKLE));
361 break;
363 case POWER_SUPPLY_PROP_HEALTH:
364 if (ec_byte & BAT_STAT_DESTROY)
365 val->intval = POWER_SUPPLY_HEALTH_DEAD;
366 else {
367 ret = olpc_bat_get_health(val);
368 if (ret)
369 return ret;
371 break;
373 case POWER_SUPPLY_PROP_MANUFACTURER:
374 ret = olpc_bat_get_mfr(val);
375 if (ret)
376 return ret;
377 break;
378 case POWER_SUPPLY_PROP_TECHNOLOGY:
379 ret = olpc_bat_get_tech(val);
380 if (ret)
381 return ret;
382 break;
383 case POWER_SUPPLY_PROP_VOLTAGE_AVG:
384 case POWER_SUPPLY_PROP_VOLTAGE_NOW:
385 ret = olpc_ec_cmd(EC_BAT_VOLTAGE, NULL, 0, (void *)&ec_word, 2);
386 if (ret)
387 return ret;
389 val->intval = (s16)be16_to_cpu(ec_word) * 9760L / 32;
390 break;
391 case POWER_SUPPLY_PROP_CURRENT_AVG:
392 case POWER_SUPPLY_PROP_CURRENT_NOW:
393 ret = olpc_ec_cmd(EC_BAT_CURRENT, NULL, 0, (void *)&ec_word, 2);
394 if (ret)
395 return ret;
397 val->intval = (s16)be16_to_cpu(ec_word) * 15625L / 120;
398 break;
399 case POWER_SUPPLY_PROP_CAPACITY:
400 ret = olpc_ec_cmd(EC_BAT_SOC, NULL, 0, &ec_byte, 1);
401 if (ret)
402 return ret;
403 val->intval = ec_byte;
404 break;
405 case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
406 if (ec_byte & BAT_STAT_FULL)
407 val->intval = POWER_SUPPLY_CAPACITY_LEVEL_FULL;
408 else if (ec_byte & BAT_STAT_LOW)
409 val->intval = POWER_SUPPLY_CAPACITY_LEVEL_LOW;
410 else
411 val->intval = POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
412 break;
413 case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
414 ret = olpc_bat_get_charge_full_design(val);
415 if (ret)
416 return ret;
417 break;
418 case POWER_SUPPLY_PROP_CHARGE_NOW:
419 ret = olpc_bat_get_charge_now(val);
420 if (ret)
421 return ret;
422 break;
423 case POWER_SUPPLY_PROP_TEMP:
424 ret = olpc_ec_cmd(EC_BAT_TEMP, NULL, 0, (void *)&ec_word, 2);
425 if (ret)
426 return ret;
428 val->intval = (s16)be16_to_cpu(ec_word) * 100 / 256;
429 break;
430 case POWER_SUPPLY_PROP_TEMP_AMBIENT:
431 ret = olpc_ec_cmd(EC_AMB_TEMP, NULL, 0, (void *)&ec_word, 2);
432 if (ret)
433 return ret;
435 val->intval = (int)be16_to_cpu(ec_word) * 100 / 256;
436 break;
437 case POWER_SUPPLY_PROP_CHARGE_COUNTER:
438 ret = olpc_ec_cmd(EC_BAT_ACR, NULL, 0, (void *)&ec_word, 2);
439 if (ret)
440 return ret;
442 val->intval = (s16)be16_to_cpu(ec_word) * 6250 / 15;
443 break;
444 case POWER_SUPPLY_PROP_SERIAL_NUMBER:
445 ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8);
446 if (ret)
447 return ret;
449 sprintf(bat_serial, "%016llx", (long long)be64_to_cpu(ser_buf));
450 val->strval = bat_serial;
451 break;
452 case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
453 ret = olpc_bat_get_voltage_max_design(val);
454 if (ret)
455 return ret;
456 break;
457 default:
458 ret = -EINVAL;
459 break;
462 return ret;
465 static enum power_supply_property olpc_xo1_bat_props[] = {
466 POWER_SUPPLY_PROP_STATUS,
467 POWER_SUPPLY_PROP_CHARGE_TYPE,
468 POWER_SUPPLY_PROP_PRESENT,
469 POWER_SUPPLY_PROP_HEALTH,
470 POWER_SUPPLY_PROP_TECHNOLOGY,
471 POWER_SUPPLY_PROP_VOLTAGE_AVG,
472 POWER_SUPPLY_PROP_VOLTAGE_NOW,
473 POWER_SUPPLY_PROP_CURRENT_AVG,
474 POWER_SUPPLY_PROP_CURRENT_NOW,
475 POWER_SUPPLY_PROP_CAPACITY,
476 POWER_SUPPLY_PROP_CAPACITY_LEVEL,
477 POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
478 POWER_SUPPLY_PROP_CHARGE_NOW,
479 POWER_SUPPLY_PROP_TEMP,
480 POWER_SUPPLY_PROP_TEMP_AMBIENT,
481 POWER_SUPPLY_PROP_MANUFACTURER,
482 POWER_SUPPLY_PROP_SERIAL_NUMBER,
483 POWER_SUPPLY_PROP_CHARGE_COUNTER,
484 POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
487 /* XO-1.5 does not have ambient temperature property */
488 static enum power_supply_property olpc_xo15_bat_props[] = {
489 POWER_SUPPLY_PROP_STATUS,
490 POWER_SUPPLY_PROP_CHARGE_TYPE,
491 POWER_SUPPLY_PROP_PRESENT,
492 POWER_SUPPLY_PROP_HEALTH,
493 POWER_SUPPLY_PROP_TECHNOLOGY,
494 POWER_SUPPLY_PROP_VOLTAGE_AVG,
495 POWER_SUPPLY_PROP_VOLTAGE_NOW,
496 POWER_SUPPLY_PROP_CURRENT_AVG,
497 POWER_SUPPLY_PROP_CURRENT_NOW,
498 POWER_SUPPLY_PROP_CAPACITY,
499 POWER_SUPPLY_PROP_CAPACITY_LEVEL,
500 POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
501 POWER_SUPPLY_PROP_CHARGE_NOW,
502 POWER_SUPPLY_PROP_TEMP,
503 POWER_SUPPLY_PROP_MANUFACTURER,
504 POWER_SUPPLY_PROP_SERIAL_NUMBER,
505 POWER_SUPPLY_PROP_CHARGE_COUNTER,
506 POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
509 /* EEPROM reading goes completely around the power_supply API, sadly */
511 #define EEPROM_START 0x20
512 #define EEPROM_END 0x80
513 #define EEPROM_SIZE (EEPROM_END - EEPROM_START)
515 static ssize_t olpc_bat_eeprom_read(struct file *filp, struct kobject *kobj,
516 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
518 uint8_t ec_byte;
519 int ret;
520 int i;
522 if (off >= EEPROM_SIZE)
523 return 0;
524 if (off + count > EEPROM_SIZE)
525 count = EEPROM_SIZE - off;
527 for (i = 0; i < count; i++) {
528 ec_byte = EEPROM_START + off + i;
529 ret = olpc_ec_cmd(EC_BAT_EEPROM, &ec_byte, 1, &buf[i], 1);
530 if (ret) {
531 pr_err("olpc-battery: "
532 "EC_BAT_EEPROM cmd @ 0x%x failed - %d!\n",
533 ec_byte, ret);
534 return -EIO;
538 return count;
541 static struct bin_attribute olpc_bat_eeprom = {
542 .attr = {
543 .name = "eeprom",
544 .mode = S_IRUGO,
546 .size = 0,
547 .read = olpc_bat_eeprom_read,
550 /* Allow userspace to see the specific error value pulled from the EC */
552 static ssize_t olpc_bat_error_read(struct device *dev,
553 struct device_attribute *attr, char *buf)
555 uint8_t ec_byte;
556 ssize_t ret;
558 ret = olpc_ec_cmd(EC_BAT_ERRCODE, NULL, 0, &ec_byte, 1);
559 if (ret < 0)
560 return ret;
562 return sprintf(buf, "%d\n", ec_byte);
565 static struct device_attribute olpc_bat_error = {
566 .attr = {
567 .name = "error",
568 .mode = S_IRUGO,
570 .show = olpc_bat_error_read,
573 /*********************************************************************
574 * Initialisation
575 *********************************************************************/
577 static struct power_supply olpc_bat = {
578 .name = "olpc-battery",
579 .get_property = olpc_bat_get_property,
580 .use_for_apm = 1,
583 static int olpc_battery_suspend(struct platform_device *pdev,
584 pm_message_t state)
586 if (device_may_wakeup(olpc_ac.dev))
587 olpc_ec_wakeup_set(EC_SCI_SRC_ACPWR);
588 else
589 olpc_ec_wakeup_clear(EC_SCI_SRC_ACPWR);
591 if (device_may_wakeup(olpc_bat.dev))
592 olpc_ec_wakeup_set(EC_SCI_SRC_BATTERY | EC_SCI_SRC_BATSOC
593 | EC_SCI_SRC_BATERR);
594 else
595 olpc_ec_wakeup_clear(EC_SCI_SRC_BATTERY | EC_SCI_SRC_BATSOC
596 | EC_SCI_SRC_BATERR);
598 return 0;
601 static int olpc_battery_probe(struct platform_device *pdev)
603 int ret;
604 uint8_t status;
607 * We've seen a number of EC protocol changes; this driver requires
608 * the latest EC protocol, supported by 0x44 and above.
610 if (olpc_platform_info.ecver < 0x44) {
611 printk(KERN_NOTICE "OLPC EC version 0x%02x too old for "
612 "battery driver.\n", olpc_platform_info.ecver);
613 return -ENXIO;
616 ret = olpc_ec_cmd(EC_BAT_STATUS, NULL, 0, &status, 1);
617 if (ret)
618 return ret;
620 /* Ignore the status. It doesn't actually matter */
622 ret = power_supply_register(&pdev->dev, &olpc_ac);
623 if (ret)
624 return ret;
626 if (olpc_board_at_least(olpc_board_pre(0xd0))) { /* XO-1.5 */
627 olpc_bat.properties = olpc_xo15_bat_props;
628 olpc_bat.num_properties = ARRAY_SIZE(olpc_xo15_bat_props);
629 } else { /* XO-1 */
630 olpc_bat.properties = olpc_xo1_bat_props;
631 olpc_bat.num_properties = ARRAY_SIZE(olpc_xo1_bat_props);
634 ret = power_supply_register(&pdev->dev, &olpc_bat);
635 if (ret)
636 goto battery_failed;
638 ret = device_create_bin_file(olpc_bat.dev, &olpc_bat_eeprom);
639 if (ret)
640 goto eeprom_failed;
642 ret = device_create_file(olpc_bat.dev, &olpc_bat_error);
643 if (ret)
644 goto error_failed;
646 if (olpc_ec_wakeup_available()) {
647 device_set_wakeup_capable(olpc_ac.dev, true);
648 device_set_wakeup_capable(olpc_bat.dev, true);
651 return 0;
653 error_failed:
654 device_remove_bin_file(olpc_bat.dev, &olpc_bat_eeprom);
655 eeprom_failed:
656 power_supply_unregister(&olpc_bat);
657 battery_failed:
658 power_supply_unregister(&olpc_ac);
659 return ret;
662 static int olpc_battery_remove(struct platform_device *pdev)
664 device_remove_file(olpc_bat.dev, &olpc_bat_error);
665 device_remove_bin_file(olpc_bat.dev, &olpc_bat_eeprom);
666 power_supply_unregister(&olpc_bat);
667 power_supply_unregister(&olpc_ac);
668 return 0;
671 static const struct of_device_id olpc_battery_ids[] = {
672 { .compatible = "olpc,xo1-battery" },
675 MODULE_DEVICE_TABLE(of, olpc_battery_ids);
677 static struct platform_driver olpc_battery_driver = {
678 .driver = {
679 .name = "olpc-battery",
680 .owner = THIS_MODULE,
681 .of_match_table = olpc_battery_ids,
683 .probe = olpc_battery_probe,
684 .remove = olpc_battery_remove,
685 .suspend = olpc_battery_suspend,
688 module_platform_driver(olpc_battery_driver);
690 MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
691 MODULE_LICENSE("GPL");
692 MODULE_DESCRIPTION("Battery driver for One Laptop Per Child 'XO' machine");