linux-kernel - Re: [PATCH v4 2/4] gpio/xilinx: Convert the driver to platform device interface

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Date:	Wed, 17 Dec 2014 12:02:53 +0100
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Michal Simek <michal.simek@...inx.com>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/4] gpio/xilinx: Convert the driver to platform device interface

Hello Alexandre

> This should not be here. The mapping and call to gpiochip_add() are
> performed by of_mm_gpiochip_add(). We should thus have a
> of_mm_gpiochip_remove() function that undoes what _add did instead of
> expected all users to do unmap themselves. Can you add a patch to your
> series that adds this function?

>
> Also I am not sure I understand why the unmapping is done only once.
> Both chips are supposed to have been added (and thus mapped) at this
> stage. Oh right I see, so this driver ends up mapping the same area
> twice! Not only are you iomapping the same area twice, you are
> unmapping it only once, and only if the chip is dual. This looks very
> broken.
>

If you look carefully you can see that it is unmapped twice if it is
called twice. iounmap is called inside the  for loop.


> Couldn't you redesign the driver the following way: only add one chip
> (since you have 1 DT node), with an extra member to track which GPIOs
> belong to the second chip (in case it is dual), and change the other
> functions to handle this.

I do not mind rearranging the driver so there is only one gpio device,
even for dual chips, but I think this should be done in a separate
patch.

What about?

1) Keep the current patchset

and then

2) Add another patchset with

  - xilinx-gpio: only one gpio device
  - add  of_mm_gpiochip_remove() to the api
  - xilinx gpio: use of_mm_gpiochip_remove
  - others: use of_mm_gpiochip_remove


Regards!




-- 
Ricardo Ribalda
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