Re: [PATCH mlx5-next v7 0/4] Dynamically assign MSI-X vectors count

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Mar 26, 2021 at 02:36:31PM -0500, Bjorn Helgaas wrote:
> On Fri, Mar 26, 2021 at 11:50:44AM -0700, Alexander Duyck wrote:
> 
> > I almost wonder if it wouldn't make sense to just partition this up to
> > handle flexible resources in the future. Maybe something like having
> > the directory setup such that you have "sriov_resources/msix/" and
> > then you could have individual files with one for the total and the
> > rest with the VF BDF naming scheme. Then if we have to, we could add
> > other subdirectories in the future to handle things like queues in the
> > future.
> 
> Subdirectories would be nice, but Greg KH said earlier in a different
> context that there's an issue with them [1].  He went on to say tools
> like udev would miss uevents for the subdirs [2].
> 
> I don't know whether that's really a problem in this case -- it
> doesn't seem like we would care about uevents for files that do MSI-X
> vector assignment.
> 
> [1] https://lore.kernel.org/linux-pci/20191121211017.GA854512@kroah.com/
> [2] https://lore.kernel.org/linux-pci/20191124170207.GA2267252@kroah.com/

You can only go "one level deep" on subdirectories tied to a 'struct
device' and have userspace tools know they are still there.  You can do
that by giving an attribute group a "name" for the directory.

Anything more than that just gets very very messy very quickly and I do
not recommend doing that at all.

thanks,

greg k-h