[PATCH] spi/pl022: Fix chipselects pointer computation

[PATCH] spi/pl022: Fix chipselects pointer computation

[Roland Stigge]

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@antcom.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

Re: [PATCH] spi/pl022: Fix chipselects pointer computation

[Linus Walleij]

On Mon, Sep 3, 2012 at 10:14 AM, Roland Stigge <stigge@antcom.de> wrote:

> 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@antcom.de>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Thanks for fixing this! And thanks to Shiraz for spotting the problem,
Mark you could add a:

Reported-by: Shiraz Hashim <shiraz.linux.kernel@gmail.com>

when applying this.

Yours,
Linus Walleij

Re: [PATCH] spi/pl022: Fix chipselects pointer computation

[Mark Brown]

On Mon, Sep 03, 2012 at 10:14:29AM +0200, Roland Stigge wrote:
> The new chip select handling via GPIO introduced a pointer computation bug:

Applied, thanks.