linux-kernel - [PATCH] spi/pl022: Fix chipselects pointer computation

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Date:	Mon,  3 Sep 2012 10:14:29 +0200
From:	Roland Stigge <stigge@...com.de>
To:	linus.walleij@...aro.org, shiraz.linux.kernel@...il.com,
	aletes.xgr@...il.com, broonie@...nsource.wolfsonmicro.com,
	grant.likely@...retlab.ca, rob.herring@...xeda.com,
	rob@...dley.net, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	spi-devel-general@...ts.sourceforge.net,
	gabriel.fernandez@...ricsson.com, lee.jones@...aro.org,
	viresh.kumar@...aro.org, sachin.verma@...co
Cc:	Roland Stigge <stigge@...com.de>
Subject: [PATCH] spi/pl022: Fix chipselects pointer computation

The new chip select handling via GPIO introduced a pointer computation bug:

	(int *) pl022 + sizeof(struct pl022)

doesn't point to the data immediately after the actual struct pl022 (as was
intended) but to a multiple of bytes after it because of the (int *) type.

Replacing the kludgy pointer arithmetic with managed memory allocation for the
chip selects.

Signed-off-by: Roland Stigge <stigge@...com.de>

---
 drivers/spi/spi-pl022.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- linux-2.6.orig/drivers/spi/spi-pl022.c
+++ linux-2.6/drivers/spi/spi-pl022.c
@@ -2053,8 +2053,7 @@ pl022_probe(struct amba_device *adev, co
 	}
 
 	/* Allocate master with space for data */
-	master = spi_alloc_master(dev, sizeof(struct pl022) + sizeof(int) *
-				  num_cs);
+	master = spi_alloc_master(dev, sizeof(struct pl022));
 	if (master == NULL) {
 		dev_err(&adev->dev, "probe - cannot alloc SPI master\n");
 		status = -ENOMEM;
@@ -2066,8 +2065,8 @@ pl022_probe(struct amba_device *adev, co
 	pl022->master_info = platform_info;
 	pl022->adev = adev;
 	pl022->vendor = id->data;
-	/* Point chipselects to allocated memory beyond the main struct */
-	pl022->chipselects = (int *) pl022 + sizeof(struct pl022);
+	pl022->chipselects = devm_kzalloc(dev, num_cs * sizeof(int),
+					  GFP_KERNEL);
 
 	/*
 	 * Bus Number Which has been Assigned to this SSP controller
--
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