Re: [PATCH 5/6] ibmvscsi: Remove unsupported host config MAD and sysfs interface

On Thu, Feb 04, 2016 at 09:48:23AM -0800, Tyrel Datwyler wrote:

On 02/04/2016 12:03 AM, Johannes Thumshirn wrote:

quoted

On Wed, Feb 03, 2016 at 05:28:33PM -0600, Tyrel Datwyler wrote:

quoted

A VIOSRP_HOST_CONFIG_TYPE management datagram (MAD) has existed in
the code for some time. From what information I've gathered from
Brian King this was likely implemented on the host side in a SLES 9
based VIOS, which is no longer supported anywhere. Further, it is
not defined in PAPR or supported by any AIX based VIOS.

Treating as bit rot and removing the sysfs interface and associated
host config code accordingly.

Doesn't removing a sysfs interface potentially break userspace code?

In the general case yes, but I feel in this case no. First, Reading from
this config attribute of a vscsi host adapter always returns nothing.
Second, any userspace code using this attribute better be checking for
the existence of config. Just a quick look for
/sys/class/scsi_host/host*/config under other host adapters on my system
I find that attribute doesn't exist for any of them.

If there is truly enough concern that somebody may actually be accessing
this useless attribute from userspace then we can still strip out the
unsupported code, but leave the attribute and return nothing directly
from the show function.

Which is what I kinda prefer. Slowly deprecate and phase out, but don't break
userspace. You never know who is writing some obscure piece of code relaying on
some sysfs attribute.

Thanks,
	Johannes

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Johannes Thumshirn                                          Storage
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