On Wed, 2015-09-30 at 15:17 +0000, Ryan Attard wrote:
> My coworkers and I were setting some enclosure states on our storage
> devices, and then reading the states back using sysfs, and came across
> the 'fault' field being set to 2. When we investigated into the ses.c
> file, we found this wonderful comment:
>
> /* For device slot and array device slot elements, byte 3 bit 6
> * is "fault sensed" while byte 3 bit 5 is "fault reqstd". As this
> * code stands these bits are shifted 4 positions right so in
> * sysfs they will appear as bits 2 and 1 respectively. Strange. */
This comment is thanks to Doug Gilbert:
commit 2a350cab9daf9a46322d83b091bb05cf54ccf6ab
Author: Douglas Gilbert <dgilb...@interlog.com>
Date: Thu Jun 9 00:27:07 2011 -0400
[SCSI] ses: requesting a fault indication
> static void ses_get_fault(struct enclosure_device *edev,
> struct enclosure_component *ecomp)
> {
> unsigned char *desc;
>
>
> desc = ses_get_page2_descriptor(edev, ecomp);
> if (desc)
> ecomp->fault = (desc[3] & 0x60) >> 4;
> }
>
> I was hoping there might be an explanation (purely for curiosity's
> sake) why it was not shifted 5 positions? Or why it wasn't exported as
> 2 fields in sysfs, each representing 1 bit in the SES page?
If I remember correctly, the desire was to keep the nybble values.
Because it's not an on off field, it didn't seem to matter much whether
the fields were 0 2 4 6 or 0 1 2 3
James
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