Re: [PATCH v2 00/13] ata,libsas: Assign the unique id used for printing earlier

[Niklas Cassel <cassel@kernel.org>]

On Thu, Jun 27, 2024 at 01:54:34PM +0100, John Garry wrote:
> On 27/06/2024 13:32, Niklas Cassel wrote:
> > On Thu, Jun 27, 2024 at 01:26:04PM +0100, John Garry wrote:
> > > On 26/06/2024 19:00, Niklas Cassel wrote:
> > > > Hello all,
> > > > 
> > > > This patch series was orginally meant to simply assign a unique id used
> > > > for printing earlier (ap->print_id), but has since grown to also include
> > > > cleanups related to ata_port_alloc() (since ap->print_id is now assigned
> > > > in ata_port_alloc()).
> > > > 
> > > 
> > > There's no real problem statement wrt print_id, telling how and why things
> > > are like they are, how it is a problem, and how it is improved in this
> > > series.
> > 
> > You are right, it is missing from the cover-letter.
> > 
> > It was there in v1:
> > https://lore.kernel.org/linux-ide/20240618153537.2687621-7-cassel@kernel.org/
> > 
> > """
> > This series moves the assignment of ap->print_id, which is used as a
> > unique id for each port, earlier, such that we can use the ata_port_*
> > print functions even before the ata_host has been registered.
> > """
> 
> OK, fine.
> 
> I see code which checks vs ap->print_id, like:
> 
> static void ata_force_link_limits(struct ata_link *link)
> {
> ...
> 		if (fe->port != -1 && fe->port != link->ap->print_id)
> 			continue;
> 
> 
> Is this all ok to deal with this print_id assignment change?
> 
> To me, it seems natural to assign a valid print_id from the alloc time, so I
> can't help but wonder it was done the current way.

ap->print_id was assigned after calling ata_host_register(), because libata
allowed a driver that did not know how many ports it had, to initially call
ata_alloc_host() with a big number of ports, and then reduce the host->n_ports
variable once it knew the actually number of ports, before calling
ata_host_register(), which would then free the "excess" ports.

This feature has actually never been used by and driver, and I remove support
for this in this series:
https://lore.kernel.org/linux-ide/20240626180031.4050226-22-cassel@kernel.org/


However, you do raise a good point...
ap->print_id is just supposed to be used for printing, but it appears that
ata_force_link_limits() and some other ata_force_*() functions make use of
it for other things... sigh...

Hopefully I can just change them from:
	if (fe->port != -1 && fe->port != link->ap->print_id)
to
	if (fe->port != -1)

but I will need to look in to this further...

Thank you for noticing this (ab)use of print_id!


Kind regards,
Niklas