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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Brian Norris <briannorris@chromium.org>,
        Salvatore Bellizzi <salvatore.bellizzi@linux.seppia.net>,
        Enrico Granata <egranata@chromium.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Enrico Granata <egranata@google.com>
Subject: [PATCH 5.2 015/144] driver core: platform: return -ENXIO for missing GpioInt
Date:   Wed, 14 Aug 2019 18:59:31 +0200
Message-Id: <20190814165800.551877117@linuxfoundation.org>
In-Reply-To: <20190814165759.466811854@linuxfoundation.org>
References: <20190814165759.466811854@linuxfoundation.org>
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From: Brian Norris <briannorris@chromium.org>

commit 46c42d844211ef5902e32aa507beac0817c585e9 upstream.

Commit daaef255dc96 ("driver: platform: Support parsing GpioInt 0 in
platform_get_irq()") broke the Embedded Controller driver on most LPC
Chromebooks (i.e., most x86 Chromebooks), because cros_ec_lpc expects
platform_get_irq() to return -ENXIO for non-existent IRQs.
Unfortunately, acpi_dev_gpio_irq_get() doesn't follow this convention
and returns -ENOENT instead. So we get this error from cros_ec_lpc:

   couldn't retrieve IRQ number (-2)

I see a variety of drivers that treat -ENXIO specially, so rather than
fix all of them, let's fix up the API to restore its previous behavior.

I reported this on v2 of this patch:

https://lore.kernel.org/lkml/20190220180538.GA42642@google.com/

but apparently the patch had already been merged before v3 got sent out:

https://lore.kernel.org/lkml/20190221193429.161300-1-egranata@chromium.org/

and the result is that the bug landed and remains unfixed.

I differ from the v3 patch by:
 * allowing for ret==0, even though acpi_dev_gpio_irq_get() specifically
   documents (and enforces) that 0 is not a valid return value (noted on
   the v3 review)
 * adding a small comment

Reported-by: Brian Norris <briannorris@chromium.org>
Reported-by: Salvatore Bellizzi <salvatore.bellizzi@linux.seppia.net>
Cc: Enrico Granata <egranata@chromium.org>
Cc: <stable@vger.kernel.org>
Fixes: daaef255dc96 ("driver: platform: Support parsing GpioInt 0 in platform_get_irq()")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Enrico Granata <egranata@google.com>
Link: https://lore.kernel.org/r/20190729204954.25510-1-briannorris@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/base/platform.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -157,8 +157,13 @@ int platform_get_irq(struct platform_dev
 	 * the device will only expose one IRQ, and this fallback
 	 * allows a common code path across either kind of resource.
 	 */
-	if (num == 0 && has_acpi_companion(&dev->dev))
-		return acpi_dev_gpio_irq_get(ACPI_COMPANION(&dev->dev), num);
+	if (num == 0 && has_acpi_companion(&dev->dev)) {
+		int ret = acpi_dev_gpio_irq_get(ACPI_COMPANION(&dev->dev), num);
+
+		/* Our callers expect -ENXIO for missing IRQs. */
+		if (ret >= 0 || ret == -EPROBE_DEFER)
+			return ret;
+	}
 
 	return -ENXIO;
 #endif