Hello Mr. Dmitry ,
On Thu, Jul 9, 2015 at 10:56 PM, Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> wrote:
> On Thu, Jul 09, 2015 at 06:41:01AM -0700, Anshul Garg wrote:
>> Use for_each_set_bit to check for set bits in bitmap
>> as it is more efficient and compact.
>> Also use bitwise and instead of expensive %
>> operation while fetching next event.
>
> It is not expensive if we are using a constant that is carefully
> selected (and it is).
>
Ok i understood now.
>>
>> Signed-off-by: Anshul Garg <aksgarg1989@xxxxxxxxx>
>> ---
>> drivers/input/misc/uinput.c | 11 ++++-------
>> 1 file changed, 4 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
>> index 421e29e..a3c15ad 100644
>> --- a/drivers/input/misc/uinput.c
>> +++ b/drivers/input/misc/uinput.c
>> @@ -319,11 +319,8 @@ static int uinput_validate_absbits(struct input_dev *dev)
>> /*
>> * Check if absmin/absmax/absfuzz/absflat are sane.
>> */
>> -
>> - for (cnt = 0; cnt < ABS_CNT; cnt++) {
>> + for_each_set_bit(cnt, dev->absbit, ABS_CNT) {
>> int min, max;
>> - if (!test_bit(cnt, dev->absbit))
>> - continue;
>>
>> min = input_abs_get_min(dev, cnt);
>> max = input_abs_get_max(dev, cnt);
>> @@ -415,8 +412,8 @@ static int uinput_setup_device(struct uinput_device *udev,
>> dev->id.vendor = user_dev->id.vendor;
>> dev->id.product = user_dev->id.product;
>> dev->id.version = user_dev->id.version;
>> -
>> - for (i = 0; i < ABS_CNT; i++) {
>> +
>> + for_each_set_bit(i, dev->absbit, ABS_CNT) {
>> input_abs_set_max(dev, i, user_dev->absmax[i]);
>> input_abs_set_min(dev, i, user_dev->absmin[i]);
>> input_abs_set_fuzz(dev, i, user_dev->absfuzz[i]);
>> @@ -493,7 +490,7 @@ static bool uinput_fetch_next_event(struct uinput_device *udev,
>> have_event = udev->head != udev->tail;
>> if (have_event) {
>> *event = udev->buff[udev->tail];
>> - udev->tail = (udev->tail + 1) % UINPUT_BUFFER_SIZE;
>> + udev->tail &= UINPUT_BUFFER_SIZE - 1;
>
> What is this exactly? And how did you test it?
>
> This chunk dropped form the patch.
>
Rest changes are using for_each_set_bit instead of for loop which
checks every bit in absbit bitmap.
In uinput_validate_absbits api
for (cnt = 0; cnt < ABS_CNT; cnt++) { -> for_each_set_bit(cnt,
dev->absbit, ABS_CNT) {
ans removing test_bit code inside loop.
In uinput_setup_device api
for (i = 0; i < ABS_CNT; i++) { - >for_each_set_bit(i, dev->absbit, ABS_CNT) {
Thanks
Anshul Garg
> Thanks.
>
> --
> 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
