netdev - Re: [PATCH 1/4] arcnet: com20020: Add com20020 io mapped version

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Date:   Fri, 18 May 2018 14:18:41 +0200
From:   Andrea Greco <andrea.greco.gapmilano@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     "Tobin C. Harding" <tobin@...orbit.com>,
        Andrea Greco <a.greco@...gma.it>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 1/4] arcnet: com20020: Add com20020 io mapped version

On 05/17/2018 10:31 PM, David Miller wrote:
> From: Andrea Greco <andrea.greco.gapmilano@...il.com>
> Date: Thu, 17 May 2018 15:05:29 +0200
>
>> + /* Will be set by userspace during if setup */
>> + dev->dev_addr[0] = 0;
>
> Hmmm... really?
>
> Also, every error path from this point forward will leak 'dev'.
>

In com20020.c found this:
/* FIXME: do this some other way! */
if (!dev->dev_addr[0])
dev->dev_addr[0] = arcnet_inb(ioaddr, 8);

NODE-ID, must be univoque, for all arcnet network.
My previews idea was take random value but, this could create a
collision over network.

A possible solution is:
In case of collision com20020 set a bit in status register.
Then peak a new NODE-ID and repeat this while correct NODE-ID is found.

Other ideas is pass it via DTS.
But suppose have 2 same product in same network, same address same problem.
For this reason i prefer left standard driver behavior.

Other ideas for solve this ?

Other question discussed with Tobin in RFC patch is:

At now a devm_ioremap is done by this driver.

Other version of this driver, PCI, PCMCIA, ISA do not remap memory.
Other implementation, use:inb outb for r/w operation.
I do a ugly #ifndef and redefine arcnet_inb in case is defined
CONFIG_ARCNET_COM20020_IO.

My proposal was:
Add relative callback arcnet_inb, arcnet_outb and friends hw struct in
arcdevice.h, then every driver set callback with required function.

Regards, Andrea