[PATCH] Fix EDAC sdram_scrub_rate read failure

[Han Pingtian <phan@redhat.com>]

If sdram scrubbing rate ins't implemented on current system, read it
will cause an error:

cat: /sys/devices/system/edac/mc//mc0/sdram_scrub_rate: Invalid argument

The eba042a81edd6baaff44831b2d719b14a6d21e58 let it returning -EINVAL,
but according to the document, it should show -1:

dram memory scrubbing rate:

        'sdram_scrub_rate'

        Read/Write attribute file that controls memory scrubbing. The scrubbing
        rate is set by writing a minimum bandwidth in bytes/sec to the attribute
        file. The rate will be translated to an internal value that gives at
        least the specified rate.

        Reading the file will return the actual scrubbing rate employed.

        If configuration fails or memory scrubbing is not implemented, the value
        of the attribute file will be -1.

Signed-off-by: Han Pingtian <phan@redhat.com>
---
 drivers/edac/edac_mc_sysfs.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 29ffa35..602fdcf 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -475,7 +475,7 @@ static ssize_t mci_sdram_scrub_rate_show(struct mem_ctl_info *mci, char *data)
 	int bandwidth = 0;
 
 	if (!mci->get_sdram_scrub_rate)
-		return -EINVAL;
+		return sprintf(date, "%d\n", -1);
 
 	bandwidth = mci->get_sdram_scrub_rate(mci);
 	if (bandwidth < 0) {
-- 
1.7.1