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Subject[PATCH v5] x86, olpc: add debugfs interface for EC commands
Date
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: Daniel Drake <dsd@laptop.org>
Cc: Paul Fox <pgf@laptop.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andres Salomon <dilinger@queued.net>
---
Documentation/ABI/testing/debugfs-olpc | 16 +++++
arch/x86/platform/olpc/olpc.c | 97 ++++++++++++++++++++++++++++++++
2 files changed, 113 insertions(+), 0 deletions(-)
create mode 100644 Documentation/ABI/testing/debugfs-olpc
v2: incorporate feedback from Andrew Morton (thanks!): documentation in
Documentation/, fixed input checking, more correct command bytes construction

v3: incorporate feedback from Ingo Molnar (thanks!): whitespace/cast fixes,
fix potential overflow when nonsense resp_bytes is passed from userspace,
add mutex to protect data and to protect against concurrent read/write, give
node name 'cmd' which is better than 'generic'

v4: really fix sign-off tags

v5: really really fix sign-off tags

diff --git a/Documentation/ABI/testing/debugfs-olpc b/Documentation/ABI/testing/debugfs-olpc
new file mode 100644
index 0000000..bd76cc6
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-olpc
@@ -0,0 +1,16 @@
+What: /sys/kernel/debug/olpc-ec/cmd
+Date: Dec 2011
+KernelVersion: 3.4
+Contact: devel@lists.laptop.org
+Description:
+
+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.
diff --git a/arch/x86/platform/olpc/olpc.c b/arch/x86/platform/olpc/olpc.c
index 7cce722..a4bee53 100644
--- a/arch/x86/platform/olpc/olpc.c
+++ b/arch/x86/platform/olpc/olpc.c
@@ -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)
}
EXPORT_SYMBOL_GPL(olpc_ec_sci_query);

+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;
+
+ mutex_lock(&ec_debugfs_cmd_lock);
+
+ 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_debugfs_resp_bytes,
+ &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);
+
+out:
+ mutex_unlock(&ec_debugfs_cmd_lock);
+ 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];
+
+ mutex_lock(&ec_debugfs_cmd_lock);
+ 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]);
+ mutex_unlock(&ec_debugfs_cmd_lock);
+ 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))
+ return;
+
+ debugfs_create_file("cmd", 0600, ec_debugfs_dir, NULL,
+ &ec_debugfs_genops);
+}
+
static int olpc_ec_suspend(void)
{
return olpc_ec_mask_write(ec_wakeup_mask);
@@ -372,6 +468,7 @@ static int __init olpc_init(void)
}

register_syscore_ops(&olpc_syscore_ops);
+ setup_debugfs();

return 0;
}
--
1.7.7.6


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