Re: [PATCH] input:Misc changes against kxtj9 v5 patch

On Tue, Jul 5, 2011 at 4:35 PM, Dmitry Torokhov
[off-list ref] wrote:

On Tue, Jul 05, 2011 at 04:19:32PM -0400, Christopher Hudson wrote:

quoted

On Tue, Jul 5, 2011 at 4:05 PM, Dmitry Torokhov
[off-list ref] wrote:

quoted

On Tue, Jul 05, 2011 at 03:55:54PM -0400, chris.hudson.comp.eng@gmail.com wrote:

quoted

From: Chris Hudson <redacted>

As requested, miscellaneous changes originally suggested by Jonathan Cameron,
patched against the original kxtj9 v5 patch.

Signed-off-by: Chris Hudson <redacted>
---
 drivers/input/misc/kxtj9.c  |   38 +++++++++++++-------------------------
 include/linux/input/kxtj9.h |   10 +---------
 2 files changed, 14 insertions(+), 34 deletions(-)

diff --git a/drivers/input/misc/kxtj9.c b/drivers/input/misc/kxtj9.c
index 7faf155..b2da841 100644
--- a/drivers/input/misc/kxtj9.c
+++ b/drivers/input/misc/kxtj9.c

@@ -71,6 +71,15 @@ static const struct {

      { 0,    ODR12_5F},
 };

+static const struct {
+     u8 g_range;
+     u8 shift;
+} kxtj9_range[] = {
+     { 0,            4 },    /* +/-2g */
+     { (1 << 3),     3 },    /* +/-4g */
+     { (1 << 4),     2 },    /* +/-8g */
+};
+
 struct kxtj9_data {
      struct i2c_client *client;
      struct kxtj9_platform_data pdata;

@@ -129,25 +138,9 @@ static void kxtj9_report_acceleration_data(struct kxtj9_data *tj9)

 static int kxtj9_update_g_range(struct kxtj9_data *tj9, u8 new_g_range)
 {
-     switch (new_g_range) {
-     case KXTJ9_G_2G:
-             tj9->shift = SHIFT_ADJ_2G;
-             break;
-
-     case KXTJ9_G_4G:
-             tj9->shift = SHIFT_ADJ_4G;
-             break;
-
-     case KXTJ9_G_8G:
-             tj9->shift = SHIFT_ADJ_8G;
-             break;
-
-     default:
-             return -EINVAL;
-     }
-
+     tj9->shift = kxtj9_range[new_g_range].shift;

This is not safe, you still need to sanitize input to make sure you do
not go beyond array boundaries.

Oops...would a simple
if (new_g_range > 2)
        return -EINVAL;
do the trick?

Or "if (new_g_range >= ARRAY_SIZE(kxtj9_range)) ..."

However, why do we use indices instead of values? I.e. why don't we
allow users to specify 2, 4 and 8 in platform data and use array to
validate the supplied value and return -EINVAL if this value is not
found?

Before we were allowing the user to specify KXTJ9_G_2G, etc, which
were bitmasks that represented each available g-range.  I think
Jonathan's intent was to optimize/clean up the update_g_range
function, but I just couldn't figure out the most efficient way to do
this.  It seems that just replacing the globally defined shift
variables with their numerical counterparts within the update_g_range
function probably gives us the best combination of efficiency and
ease-of-use.

--
Dmitry

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