On 02/19/2013 02:50 PM, Borislav Petkov wrote:
On Tue, Feb 19, 2013 at 03:38:09PM +0200, Felipe Balbi wrote:
because changing the permission will cause the same issue:

Actually, I take that back. Mauro's patch will already create the file
anyway:

        if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate)

Adjusting the permissions is simply the last missing piece to this patch
to make the interface to userspace 100% coherent.

--
From: Mauro Carvalho Chehab <mche...@redhat.com>
Date: Tue, 19 Feb 2013 09:16:10 -0300
Subject: [PATCH] EDAC: only create sdram_scrub_rate where supported

Currently, sdram_scrub_rate sysfs node is created even if the device
doesn't support get/set the scub rate. Change the logic to only
create this device node when the operation is supported.

If only read or only write is supported, it will keep returning -ENODEV
just like before.

Reported-by: Felipe Balbi <ba...@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mche...@redhat.com>
---
  drivers/edac/edac_mc_sysfs.c | 21 +++++++++++++++++++--
  1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 0ca1ca71157f..5a788e60ff67 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -7,7 +7,7 @@
   *
   * Written Doug Thompson <nor...@xmission.com> www.softwarebitmaker.com
   *
- * (c) 2012 - Mauro Carvalho Chehab <mche...@redhat.com>
+ * (c) 2012-2013 - Mauro Carvalho Chehab <mche...@redhat.com>
   *    The entire API were re-written, and ported to use struct device
   *
   */
@@ -878,7 +878,6 @@ static struct attribute *mci_attrs[] = {
        &dev_attr_ce_noinfo_count.attr,
        &dev_attr_ue_count.attr,
        &dev_attr_ce_count.attr,
-       &dev_attr_sdram_scrub_rate.attr,
        &dev_attr_max_location.attr,
        NULL
  };
@@ -1012,6 +1011,23 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info 
*mci)
                return err;
        }

+       if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate) {
+               umode_t mode = 0;
+
+               if (mci->get_sdram_scrub_rate)
+                       mode = S_IRUGO;
+
+               if (mci->set_sdram_scrub_rate)
+                       mode |= S_IWUSR;
+
+               dev_attr_sdram_scrub_rate.attr.mode = mode;
+
+               err = device_create_file(&mci->dev, &dev_attr_sdram_scrub_rate);
+               if (err) {
+                       edac_dbg(1, "failure: create sdram_scrub_rate\n");
+                       goto fail2;
+               }
+       }
        /*
         * Create the dimm/rank devices
         */
@@ -1056,6 +1072,7 @@ fail:
                        continue;
                device_unregister(&dimm->dev);
        }
+fail2:
        device_unregister(&mci->dev);
        bus_unregister(&mci->bus);
        kfree(mci->bus.name);

And of course you all know that creating sysfs attributes via 'device_create_file' opens all sort of funny race conditions, especially when checking these attributes from udev ...

Please consider adding a default attribute which return '-EINVAL' or somesuch when the function pointers are not set.
But _not_ adding it via device_create_file(). That's evil.

Cheers,

Hannes
--
Dr. Hannes Reinecke                   zSeries & Storage
h...@suse.de                          +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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