gsmi: Fix bug in append_to_eventlog sysfs handler

The sysfs handler should return the number of bytes consumed, which in the
case of a successful write is the entire buffer.  Also fix a bug where
param.data_len was being set to (count - (2 * sizeof(u32))) instead of just
(count - sizeof(u32)).  The latter is correct because we skip over the
leading u32 which is our param.type, but we were also incorrectly
subtracting sizeof(u32) on the line where we were actually setting
param.data_len:

	param.data_len = count - sizeof(u32);

This meant that for our example event.kernel_software_watchdog with total
length 10 bytes, param.data_len was just 2 prior to this change.

To test, successfully append an event to the log with gsmi sysfs.
This sample event is for a "Kernel Software Watchdog"

> xxd -g 1 event.kernel_software_watchdog
0000000: 01 00 00 00 ad de 06 00 00 00

> cat event.kernel_software_watchdog > /sys/firmware/gsmi/append_to_eventlog

> mosys eventlog list | tail -1
14 | 2012-06-25 10:14:14 | Kernl Event | Software Watchdog

Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
Signed-off-by: Furquan Shaikh <furquan@google.com>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
[zwisler: updated changelog for 2nd bug fix and upstream]
Signed-off-by: Ross Zwisler <zwisler@google.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c
index 734146eec1b902373d06a057c6213049418fa8da..3677d511f4c40919341473079c1ec77b7592c2fa 100644 (file)
--- a/drivers/firmware/google/gsmi.c
+++ b/drivers/firmware/google/gsmi.c
@@ -480,11 +480,10 @@ static ssize_t eventlog_write(struct file *filp, struct kobject *kobj,
        if (count < sizeof(u32))
                return -EINVAL;
        param.type = *(u32 *)buf;
-       count -= sizeof(u32);
        buf += sizeof(u32);
 
        /* The remaining buffer is the data payload */
-       if (count > gsmi_dev.data_buf->length)
+       if ((count - sizeof(u32)) > gsmi_dev.data_buf->length)
                return -EINVAL;
        param.data_len = count - sizeof(u32);
 
@@ -504,7 +503,7 @@ static ssize_t eventlog_write(struct file *filp, struct kobject *kobj,
 
        spin_unlock_irqrestore(&gsmi_dev.lock, flags);
 
-       return rc;
+       return (rc == 0) ? count : rc;
 
 }