Re: [PATCH 5/6] lightnvm: expose device geometry through sysfs

[Matias BjÃrling]

On 06/30/2016 10:01 PM, J Freyensee wrote:
> On Wed, 2016-06-29 at 16:51 +0200, Matias BjÃrling wrote:
> > From: "Simon A. F. Lund" <slund@xxxxxxxxxxxx>
> >
> > For a host to access an Open-Channel SSD, it has to know its
> > geometry,
> > so that it writes and reads at the appropriate device bounds.
> >
> > Currently, the geometry information is kept within the kernel, and
> > not
> > exported to user-space for consumption. This patch exposes the
> > configuration through sysfs and enables user-space libraries, such as
> > liblightnvm, to use the sysfs implementation to get the geometry of
> > an
> > Open-Channel SSD.
> >
> > The sysfs entries are stored within the device hierarchy, and can be
> > found using the "lightnvm" device type.
> >
> > An example configuration looks like this:
> >
> > /sys/class/nvme/
> > âââ nvme0n1
> >     âââ capabilities: 3
> >     âââ device_mode: 1
> >     âââ channel_parallelism: 0
> >     âââ erase_max: 1000000
> >     âââ erase_typ: 1000000
> >     âââ flash_media_type: 0
> >     âââ media_capabilities: 0x00000001
> >     âââ media_type: 0
> >     âââ multiplane: 0x00010101
> >     âââ num_blocks: 1022
> >     âââ num_channels: 1
> >     âââ num_luns: 4
> >     âââ num_pages: 64
> >     âââ num_planes: 1
> >     âââ page_size: 4096
> >     âââ prog_max: 100000
> >     âââ prog_typ: 100000
> >     âââ read_max: 10000
> >     âââ read_typ: 10000
> >     âââ sector_oob_size: 0
> >     âââ sector_size: 4096
> >     âââ media_manager: gennvm
> >     âââ ppa_format: 0x380830082808001010102008
> >     âââ vendor_opcode: 0
> >     âââ version: 1
>
> That is an awful lot of new things to add under nvme0n1-type sysfs
> entries when there is already a decent amount of stuff under it.

You are right. These are rightfully placed under /lightnvm in the sysfs 
path. The description is wrong, will update it. Thanks Jay.

> Any chance these new things could be stuck under a separate sysfs
> directory under each nvmeXnY device?  If these things are mainly
> beneficial to LightNVM, it will be easier for a LightNVM newbie to
> find, recognize, and consider all the important things in an Open
> Channel SSD solution if it's under a separate directory.  And for
> current SSD solutions that don't seem to need these things exposed in
> sysfs for operation, it will make what is directly under nvmeXnY
> directories less cluttered.
>
> Thanks,
> Jay