linux-kernel - [PATCH 2/2] pinctrl: at91: add FIXME about read back of struct gpio

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Message-Id: <20250507-gpio-chip-base-readback-v1-2-ade56e38480b@pengutronix.de>
Date: Wed, 07 May 2025 19:28:02 +0200
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>, 
 Alexandre Belloni <alexandre.belloni@...tlin.com>, 
 Claudiu Beznea <claudiu.beznea@...on.dev>, 
 Ludovic Desroches <ludovic.desroches@...rochip.com>, 
 linux-gpio@...r.kernel.org, kernel@...gutronix.de, 
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 Ahmad Fatoum <a.fatoum@...gutronix.de>
Subject: [PATCH 2/2] pinctrl: at91: add FIXME about read back of struct
 gpio_chip::base

drivers/gpio/gpiolib.c has this:

  /*
   * TODO: it should not be necessary to reflect the
   * assigned base outside of the GPIO subsystem. Go over
   * drivers and see if anyone makes use of this, else
   * drop this and assign a poison instead.
   */
  gc->base = base;

This would break the driver, because it assumes gpio_chip::base to be
the same static base that was written into it.

Point that out in a comment, until it's fixed.

Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
---
 drivers/pinctrl/pinctrl-at91.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-at91.c b/drivers/pinctrl/pinctrl-at91.c
index 93ab277d9943cff3a0b771f3e997594cb144826c..b0e00f3793312de2288aa1b900793d9e2b6125d6 100644
--- a/drivers/pinctrl/pinctrl-at91.c
+++ b/drivers/pinctrl/pinctrl-at91.c
@@ -949,6 +949,11 @@ static int at91_gpio_request_enable(struct pinctrl_dev *pctldev,
 
 	dev_dbg(npct->dev, "enable pin %u as GPIO\n", offset);
 
+	/*
+	 * The GPIO chip base is an internal detail that will
+	 * eventually go away alongside sysfs and the global numberspace.
+	 * FIXME: stop reading it back here
+	 */
 	mask = 1 << (offset - chip->base);
 
 	dev_dbg(npct->dev, "enable pin %u as PIO%c%d 0x%x\n",

-- 
2.39.5