linux-kernel - Re: [PATCH 2/4] net: sfp: allow to use also SFP modules which are detected as SFF

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Date:   Thu, 31 Dec 2020 14:52:43 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Marek Behún <kabel@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] net: sfp: allow to use also SFP modules which are
 detected as SFF

On Wednesday 30 December 2020 19:12:40 Russell King - ARM Linux admin wrote:
> On Wed, Dec 30, 2020 at 06:27:07PM +0100, Marek Behún wrote:
> > On Wed, 30 Dec 2020 18:06:52 +0100
> > Pali Rohár <pali@...nel.org> wrote:
> > 
> > > 	if (!sfp->type->module_supported(&id) &&
> > > 	    (memcmp(id.base.vendor_name, "UBNT            ", 16) ||
> > > 	     memcmp(id.base.vendor_pn, "UF-INSTANT      ", 16)))
> > 
> > I would rather add a quirk member (bitfield) to the sfp structure and do
> > something like this
> > 
> > if (!sfp->type->module_supported(&id) &&
> >     !(sfp->quirks & SFP_QUIRK_BAD_PHYS_ID))
> > 
> > or maybe put this check into the module_supported method.
> 
> Sorry, definitely not. If you've ever looked at the SDHCI driver with
> its multiple "quirks" bitfields, doing this is a recipe for creating
> a very horrid hard to understand mess.
> 
> What you suggest just results in yet more complexity.

Should I rather put this vendor name/pn check into the
sfp_module_supported() function?

static bool sfp_module_supported(const struct sfp_eeprom_id *id)
{
	if (id->base.phys_id == SFF8024_ID_SFP &&
	    id->base.phys_ext_id == SFP_PHYS_EXT_ID_SFP)
		return true;

	if (id->base.phys_id == SFF8024_ID_SFF_8472 &&
	    id->base.phys_ext_id == SFP_PHYS_EXT_ID_SFP &&
	    !memcmp(id->base.vendor_name, "UBNT            ", 16) &&
	    !memcmp(id->base.vendor_pn, "UF-INSTANT      ", 16))
		return true;

	return false;
}