On Sun, Feb 21, 2021 at 08:59:18AM +0200, Leon Romanovsky wrote:

On Sat, Feb 20, 2021 at 01:06:00PM -0600, Bjorn Helgaas wrote:

quoted

On Fri, Feb 19, 2021 at 09:20:18AM +0100, Greg Kroah-Hartman wrote:

quoted

Ok, can you step back and try to explain what problem you are trying to
solve first, before getting bogged down in odd details?  I find it
highly unlikely that this is something "unique", but I could be wrong as
I do not understand what you are wanting to do here at all.

We want to add two new sysfs files:

  sriov_vf_total_msix, for PF devices
  sriov_vf_msix_count, for VF devices associated with the PF

AFAICT it is *acceptable* if they are both present always.  But it
would be *ideal* if they were only present when a driver that
implements the ->sriov_get_vf_total_msix() callback is bound to the
PF.

BTW, we already have all possible combinations: static, static with
folder, with and without "sriov_" prefix, dynamic with and without
folders on VFs.

I need to know on which version I'll get Acked-by and that version I
will resubmit.

I propose that you make static attributes for both files, so
"sriov_vf_total_msix" is visible for *every* PF in the system and
"sriov_vf_msix_count" is visible for *every* VF in the system.

The PF "sriov_vf_total_msix" show function can return zero if there's
no PF driver or it doesn't support ->sriov_get_vf_total_msix().
(Incidentally, I think the documentation should mention that when it
*is* supported, the contents of this file are *constant*, i.e., it
does not decrease as vectors are assigned to VFs.)

The "sriov_vf_msix_count" set function can ignore writes if there's no
PF driver or it doesn't support ->sriov_get_vf_total_msix(), or if a
VF driver is bound.

Any userspace software must be able to deal with those scenarios
anyway, so I don't think the mere presence or absence of the files is
a meaningful signal to that software.

If we figure out a way to make the files visible only when the
appropriate driver is bound, that might be nice and could always be
done later.  But I don't think it's essential.

Bjorn