On Fri, Jan 3, 2014 at 9:28 PM, Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> wrote:
> pcu->cmd_buf[IMS_PCU_DATA_OFFSET] is word aligned so we do not need to use
> get_unaligned_le16 to access it.
>
> Also let's add build time check to make sure it stays aligned.
- AFAIK, there's no guarantee the "pcu" itself is aligned
- This change assumes that aligning data on the 2-byte boundary is
sufficient for all architectures that do not allow unaligned data
access, which I don't think is a good assumption to make
- On x86 or any other architecture that allows unaligned access
get_unaligned_le16() is actually results to call to le16_to_cpup(), so
this change doesn't really save anything while imposing restrictions
on the arrangement of the fields in struct ims_pcu and causing
unnecessary build errors.
So, for what its worth, NACK for this patch from me.
>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> ---
> drivers/input/misc/ims-pcu.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c
> index 513ecdf..b8f1029 100644
> --- a/drivers/input/misc/ims-pcu.c
> +++ b/drivers/input/misc/ims-pcu.c
> @@ -116,6 +116,8 @@ struct ims_pcu {
> bool setup_complete; /* Input and LED devices have been created */
> };
>
> +#define IMS_PCU_CHECK_CMD_BUF_ALIGNMENT(offset, alignment) \
> + IS_ALIGNED(offsetof(struct ims_pcu, cmd_buf[offset]), alignment)
>
> /*********************************************************************
> * Buttons Input device support *
> @@ -999,8 +1001,10 @@ ims_pcu_backlight_get_brightness(struct led_classdev *cdev)
> /* Assume the LED is OFF */
> brightness = LED_OFF;
> } else {
> - brightness =
> - get_unaligned_le16(&pcu->cmd_buf[IMS_PCU_DATA_OFFSET]);
> + BUILD_BUG_ON(!IMS_PCU_CHECK_CMD_BUF_ALIGNMENT(
> + IMS_PCU_DATA_OFFSET, 2));
> + brightness = le16_to_cpup(
> + (__le16 *)&pcu->cmd_buf[IMS_PCU_DATA_OFFSET]);
> }
>
> mutex_unlock(&pcu->cmd_mutex);
> --
> 1.8.4.2
>
>
> --
> Dmitry
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
