Commit a3c8121b authored by Daniel Drake's avatar Daniel Drake Committed by Ingo Molnar
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x86/olpc: Add debugfs interface for EC commands

Add a debugfs interface for sending commands to the OLPC
Embedded Controller (EC) and reading the responses.  The EC
provides functionality for machine identification, battery and
AC control, wakeup control, etc.

Having a debugfs interface available is useful for EC
development and debugging.

Based on code by Paul Fox (who also approves of the end result).

Signed-off-by: default avatarDaniel Drake <>
Acked-by: default avatarPaul Fox <>
Cc: "H. Peter Anvin" <>
Cc: Andres Salomon <>

Signed-off-by: default avatarIngo Molnar <>
parent 90e24014
What: /sys/kernel/debug/olpc-ec/cmd
Date: Dec 2011
KernelVersion: 3.4
A generic interface for executing OLPC Embedded Controller commands and
reading their responses.
To execute a command, write data with the format: CC:N A A A A
CC is the (hex) command, N is the count of expected reply bytes, and A A A A
are optional (hex) arguments.
To read the response (if any), read from the generic node after executing
a command. Hex reply bytes will be returned, *whether or not* they came from
the immediately previous command.
......@@ -20,6 +20,8 @@
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/syscore_ops.h>
#include <linux/debugfs.h>
#include <linux/mutex.h>
#include <asm/geode.h>
#include <asm/setup.h>
......@@ -31,6 +33,15 @@ EXPORT_SYMBOL_GPL(olpc_platform_info);
static DEFINE_SPINLOCK(ec_lock);
/* debugfs interface to EC commands */
#define EC_MAX_CMD_ARGS (5 + 1) /* cmd byte + 5 args */
#define EC_MAX_CMD_REPLY (8)
static struct dentry *ec_debugfs_dir;
static DEFINE_MUTEX(ec_debugfs_cmd_lock);
static unsigned char ec_debugfs_resp[EC_MAX_CMD_REPLY];
static unsigned int ec_debugfs_resp_bytes;
/* EC event mask to be applied during suspend (defining wakeup sources). */
static u16 ec_wakeup_mask;
......@@ -269,6 +280,91 @@ int olpc_ec_sci_query(u16 *sci_value)
static ssize_t ec_debugfs_cmd_write(struct file *file, const char __user *buf,
size_t size, loff_t *ppos)
int i, m;
unsigned char ec_cmd[EC_MAX_CMD_ARGS];
unsigned int ec_cmd_int[EC_MAX_CMD_ARGS];
char cmdbuf[64];
int ec_cmd_bytes;
size = simple_write_to_buffer(cmdbuf, sizeof(cmdbuf), ppos, buf, size);
m = sscanf(cmdbuf, "%x:%u %x %x %x %x %x", &ec_cmd_int[0],
&ec_cmd_int[1], &ec_cmd_int[2], &ec_cmd_int[3],
&ec_cmd_int[4], &ec_cmd_int[5]);
if (m < 2 || ec_debugfs_resp_bytes > EC_MAX_CMD_REPLY) {
/* reset to prevent overflow on read */
ec_debugfs_resp_bytes = 0;
printk(KERN_DEBUG "olpc-ec: bad ec cmd: "
"cmd:response-count [arg1 [arg2 ...]]\n");
size = -EINVAL;
goto out;
/* convert scanf'd ints to char */
ec_cmd_bytes = m - 2;
for (i = 0; i <= ec_cmd_bytes; i++)
ec_cmd[i] = ec_cmd_int[i];
printk(KERN_DEBUG "olpc-ec: debugfs cmd 0x%02x with %d args "
"%02x %02x %02x %02x %02x, want %d returns\n",
ec_cmd[0], ec_cmd_bytes, ec_cmd[1], ec_cmd[2], ec_cmd[3],
ec_cmd[4], ec_cmd[5], ec_debugfs_resp_bytes);
olpc_ec_cmd(ec_cmd[0], (ec_cmd_bytes == 0) ? NULL : &ec_cmd[1],
ec_cmd_bytes, ec_debugfs_resp, ec_debugfs_resp_bytes);
printk(KERN_DEBUG "olpc-ec: response "
"%02x %02x %02x %02x %02x %02x %02x %02x (%d bytes expected)\n",
ec_debugfs_resp[0], ec_debugfs_resp[1], ec_debugfs_resp[2],
ec_debugfs_resp[3], ec_debugfs_resp[4], ec_debugfs_resp[5],
ec_debugfs_resp[6], ec_debugfs_resp[7], ec_debugfs_resp_bytes);
return size;
static ssize_t ec_debugfs_cmd_read(struct file *file, char __user *buf,
size_t size, loff_t *ppos)
unsigned int i, r;
char *rp;
char respbuf[64];
rp = respbuf;
rp += sprintf(rp, "%02x", ec_debugfs_resp[0]);
for (i = 1; i < ec_debugfs_resp_bytes; i++)
rp += sprintf(rp, ", %02x", ec_debugfs_resp[i]);
rp += sprintf(rp, "\n");
r = rp - respbuf;
return simple_read_from_buffer(buf, size, ppos, respbuf, r);
static const struct file_operations ec_debugfs_genops = {
.write = ec_debugfs_cmd_write,
.read = ec_debugfs_cmd_read,
static void setup_debugfs(void)
ec_debugfs_dir = debugfs_create_dir("olpc-ec", 0);
if (ec_debugfs_dir == ERR_PTR(-ENODEV))
debugfs_create_file("cmd", 0600, ec_debugfs_dir, NULL,
static int olpc_ec_suspend(void)
return olpc_ec_mask_write(ec_wakeup_mask);
......@@ -372,6 +468,7 @@ static int __init olpc_init(void)
return 0;
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