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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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