[PATCH v2] media: cx18, ivtv: eliminate unnecessary array index checks

[PATCH v2] media: cx18, ivtv: eliminate unnecessary array index checks

[Nickolai Zeldovich]

The idx values passed to cx18_i2c_register() and ivtv_i2c_register()
by cx18_init_subdevs() and ivtv_load_and_init_modules() respectively
are always in-range, based on how the hw_all bitmask is populated.
Previously, the checks were already ineffective because arrays were
being dereferenced using the index before the check.

Signed-off-by: Nickolai Zeldovich <nickolai@csail.mit.edu>
---
Thanks to Andy Walls for suggesting that instead of moving the checks
before array dereference, a better fix is to remove the checks altogether,
since they are superfluous.

 drivers/media/pci/cx18/cx18-i2c.c |    3 ---
 drivers/media/pci/ivtv/ivtv-i2c.c |    2 --
 2 files changed, 5 deletions(-)

diff --git a/drivers/media/pci/cx18/cx18-i2c.c b/drivers/media/pci/cx18/cx18-i2c.c
index 4908eb7..ccb1d15 100644
--- a/drivers/media/pci/cx18/cx18-i2c.c
+++ b/drivers/media/pci/cx18/cx18-i2c.c
@@ -116,9 +116,6 @@ int cx18_i2c_register(struct cx18 *cx, unsigned idx)
 	const char *type = hw_devicenames[idx];
 	u32 hw = 1 << idx;
 
-	if (idx >= ARRAY_SIZE(hw_addrs))
-		return -1;
-
 	if (hw == CX18_HW_TUNER) {
 		/* special tuner group handling */
 		sd = v4l2_i2c_new_subdev(&cx->v4l2_dev,
diff --git a/drivers/media/pci/ivtv/ivtv-i2c.c b/drivers/media/pci/ivtv/ivtv-i2c.c
index 46e262b..bc984af 100644
--- a/drivers/media/pci/ivtv/ivtv-i2c.c
+++ b/drivers/media/pci/ivtv/ivtv-i2c.c
@@ -267,8 +267,6 @@ int ivtv_i2c_register(struct ivtv *itv, unsigned idx)
 	const char *type = hw_devicenames[idx];
 	u32 hw = 1 << idx;
 
-	if (idx >= ARRAY_SIZE(hw_addrs))
-		return -1;
 	if (hw == IVTV_HW_TUNER) {
 		/* special tuner handling */
 		sd = v4l2_i2c_new_subdev(&itv->v4l2_dev, adap, type, 0,
-- 
1.7.10.4

Re: [PATCH v2] media: cx18, ivtv: eliminate unnecessary array index checks

[Andy Walls]

Nickolai Zeldovich <nickolai@csail.mit.edu> wrote:

>The idx values passed to cx18_i2c_register() and ivtv_i2c_register()
>by cx18_init_subdevs() and ivtv_load_and_init_modules() respectively
>are always in-range, based on how the hw_all bitmask is populated.
>Previously, the checks were already ineffective because arrays were
>being dereferenced using the index before the check.
>
>Signed-off-by: Nickolai Zeldovich <nickolai@csail.mit.edu>
>---
>Thanks to Andy Walls for suggesting that instead of moving the checks
>before array dereference, a better fix is to remove the checks
>altogether,
>since they are superfluous.
>
> drivers/media/pci/cx18/cx18-i2c.c |    3 ---
> drivers/media/pci/ivtv/ivtv-i2c.c |    2 --
> 2 files changed, 5 deletions(-)
>
>diff --git a/drivers/media/pci/cx18/cx18-i2c.c
>b/drivers/media/pci/cx18/cx18-i2c.c
>index 4908eb7..ccb1d15 100644
>--- a/drivers/media/pci/cx18/cx18-i2c.c
>+++ b/drivers/media/pci/cx18/cx18-i2c.c
>@@ -116,9 +116,6 @@ int cx18_i2c_register(struct cx18 *cx, unsigned
>idx)
> 	const char *type = hw_devicenames[idx];
> 	u32 hw = 1 << idx;
> 
>-	if (idx >= ARRAY_SIZE(hw_addrs))
>-		return -1;
>-
> 	if (hw == CX18_HW_TUNER) {
> 		/* special tuner group handling */
> 		sd = v4l2_i2c_new_subdev(&cx->v4l2_dev,
>diff --git a/drivers/media/pci/ivtv/ivtv-i2c.c
>b/drivers/media/pci/ivtv/ivtv-i2c.c
>index 46e262b..bc984af 100644
>--- a/drivers/media/pci/ivtv/ivtv-i2c.c
>+++ b/drivers/media/pci/ivtv/ivtv-i2c.c
>@@ -267,8 +267,6 @@ int ivtv_i2c_register(struct ivtv *itv, unsigned
>idx)
> 	const char *type = hw_devicenames[idx];
> 	u32 hw = 1 << idx;
> 
>-	if (idx >= ARRAY_SIZE(hw_addrs))
>-		return -1;
> 	if (hw == IVTV_HW_TUNER) {
> 		/* special tuner handling */
> 		sd = v4l2_i2c_new_subdev(&itv->v4l2_dev, adap, type, 0,
>-- 
>1.7.10.4

Acked-by: Andy Walls <awalls@md.metrocast.net>