netdev - Re: [RFC 0/6] pcmcia: separate 16-bit support from cardbus

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Message-ID: <3d8f28d7-78df-5276-612c-85b5262a987a@lwfinger.net>
Date:   Mon, 27 Feb 2023 14:23:56 -0600
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Arnd Bergmann <arnd@...nel.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        linux-kernel@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Ian Abbott <abbotti@....co.uk>,
        Jakub Kicinski <kuba@...nel.org>,
        Kevin Cernekee <cernekee@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        Manuel Lauss <manuel.lauss@...il.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Olof Johansson <olof@...om.net>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        YOKOTA Hiroshi <yokota@...lab.is.tsukuba.ac.jp>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org, linux-can@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC 0/6] pcmcia: separate 16-bit support from cardbus

On 2/27/23 07:34, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Based on some recent discussions [1][2][3], I experimented wtih what
> drivers/pcmcia would look like if we completely removed 16-bit support,
> which was one of the options that Dominik suggested for winding down
> pcmcia maintenance.
> 
> The remaining cardbus/yenta support is essentially a PCI hotplug driver
> with a slightly unusual sysfs interface, and it would still support all
> 32-bit cardbus hosts and cards, but no longer work with the even older
> 16-bit cards that require the pcmcia_driver infrastructure.
> 
> I don't expect this to be a problem normal laptop support, as the last
> PC models that predate Cardbus support (e.g. 1997 ThinkPad 380ED) are
> all limited to i586MMX CPUs and 80MB of RAM. This is barely enough to
> boot Tiny Core Linux but not a regular distro.
> 
> Support for device drivers is somewhat less clear. Losing support for
> 16-bit cards in cardbus sockets is obviously a limiting factor for
> anyone who still has those cards, but there is also a good chance that
> the only reason to keep the cards around is for using them in pre-cardbus
> machines that cannot be upgrade to 32-bit devices.
> 
> Completely removing the 16-bit PCMCIA support would however break some
> 20+ year old embedded machines that rely on CompactFlash cards as their
> mass-storage device (extension), this notably includes early PocketPC
> models and the reference implementations for OMAP1, StrongARM1100,
> Alchemy and PA-Semi. All of these are still maintained, though most
> of the PocketPC machines got removed in the 6.3 merge window and the
> PA-Semi Electra board is the only one that was introduced after
> 2003.
> 
> The approach that I take in this series is to split drivers/pcmcia
> into two mutually incompatible parts: the Cardbus support contains
> all the code that is relevant for post-1997 laptops and gets moved
> to drivers/pci/hotplug, while the drivers/pcmcia/ subsystem is
> retained for both the older laptops and the embedded systems but no
> longer works with the yenta socket host driver. The BCM63xx
> PCMCIA/Cardbus host driver appears to be unused and conflicts with
> this series, so it is removed in the process.
> 
> My series does not touch any of the pcmcia_driver instances, but
> if there is consensus about splitting out the cardbus support,
> a lot of them can probably get removed as a follow-up.

Arnd,

Your patch set also breaks my PowerBook G4. The output of 'lspci -nn | grep 
Network' shows the following before your patch is applied:

0001:10:12.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4306 
802.11b/g Wireless LAN Controller [14e4:4320] (rev 03)
0001:11:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4318 
[AirForce One 54g] 802.11g Wireless LAN Controller [14e4:4318] (rev 02)

The first of these is broken and built into the laptop. The second is plugged 
into a PCMCIA slot, and uses yenta-socket as a driver.

When your patches are applied, the second entry vanishes.

Yes, this hardware is ancient, but I would prefer having this wifi interface 
work. I can provide any output you need.

Larry