Re: [PATCH v1 5/5] gpiolib: cdev: Utilize more bitmap APIs

Yury Norov
2023-09-27T03:07:10Z

On Tue, Sep 26, 2023 at 08:20:07AM +0300, Andy Shevchenko wrote:
> Currently we have a few bitmap calls that are open coded in the library
> module. Let's convert them to use generic bitmap APIs instead.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> drivers/gpio/gpiolib-cdev.c | 79 +++++++++++++++++--------------------
> 1 file changed, 36 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index e39d344feb28..a5bbbd44531f 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -1263,35 +1263,32 @@ static long linereq_get_values(struct linereq *lr, void __user *ip)
> {
> struct gpio_v2_line_values lv;
> DECLARE_BITMAP(vals, GPIO_V2_LINES_MAX);
> + DECLARE_BITMAP(mask, GPIO_V2_LINES_MAX);
> + DECLARE_BITMAP(bits, GPIO_V2_LINES_MAX);
> struct gpio_desc **descs;
> unsigned int i, didx, num_get;
> - bool val;
> int ret;
>
> /* NOTE: It's ok to read values of output lines. */
> if (copy_from_user(&lv, ip, sizeof(lv)))
> return -EFAULT;
>
> - for (num_get = 0, i = 0; i < lr->num_lines; i++) {
> - if (lv.mask & BIT_ULL(i)) {
> - num_get++;
> - descs = &lr->lines[i].desc;
> - }
> - }
> + bitmap_from_arr64(mask, &lv.mask, GPIO_V2_LINES_MAX);
>
> + num_get = bitmap_weight(mask, lr->num_lines);
> if (num_get == 0)
> return -EINVAL;
>
> - if (num_get != 1) {
> + if (num_get == 1) {
> + descs = &lr->lines[find_first_bit(mask, lr->num_lines)].desc;
> + } else {
> descs = kmalloc_array(num_get, sizeof(*descs), GFP_KERNEL);
> if (!descs)
> return -ENOMEM;
> - for (didx = 0, i = 0; i < lr->num_lines; i++) {
> - if (lv.mask & BIT_ULL(i)) {
> - descs[didx] = lr->lines[i].desc;
> - didx++;
> - }
> - }
> +
> + didx = 0;
> + for_each_set_bit(i, mask, lr->num_lines)
> + descs[didx++] = lr->lines[i].desc;
> }
> ret = gpiod_get_array_value_complex(false, true, num_get,
> descs, NULL, vals);
> @@ -1301,19 +1298,15 @@ static long linereq_get_values(struct linereq *lr, void __user *ip)
> if (ret)
> return ret;
>
> - lv.bits = 0;
> - for (didx = 0, i = 0; i < lr->num_lines; i++) {
> - if (lv.mask & BIT_ULL(i)) {
> - if (lr->lines[i].sw_debounced)
> - val = debounced_value(&lr->lines[i]);
> - else
> - val = test_bit(didx, vals);
> - if (val)
> - lv.bits |= BIT_ULL(i);
> - didx++;
> - }
> + bitmap_scatter(bits, vals, mask, lr->num_lines);
> +
> + for_each_set_bit(i, mask, lr->num_lines) {
> + if (lr->lines[i].sw_debounced)
> + __assign_bit(i, bits, debounced_value(&lr->lines[i]));
> }
>
> + bitmap_to_arr64(&lv.bits, bits, GPIO_V2_LINES_MAX);
> +
> if (copy_to_user(ip, &lv, sizeof(lv)))
> return -EFAULT;
>
> @@ -1324,35 +1317,35 @@ static long linereq_set_values_unlocked(struct linereq *lr,
> struct gpio_v2_line_values *lv)
> {
> DECLARE_BITMAP(vals, GPIO_V2_LINES_MAX);
> + DECLARE_BITMAP(mask, GPIO_V2_LINES_MAX);
> + DECLARE_BITMAP(bits, GPIO_V2_LINES_MAX);
> struct gpio_desc **descs;
> unsigned int i, didx, num_set;
> int ret;
>
> - bitmap_zero(vals, GPIO_V2_LINES_MAX);
> - for (num_set = 0, i = 0; i < lr->num_lines; i++) {
> - if (lv->mask & BIT_ULL(i)) {
> - if (!test_bit(FLAG_IS_OUT, &lr->lines[i].desc->flags))
> - return -EPERM;
> - if (lv->bits & BIT_ULL(i))
> - __set_bit(num_set, vals);
> - num_set++;
> - descs = &lr->lines[i].desc;
> - }
> - }
> + bitmap_from_arr64(mask, &lv->mask, GPIO_V2_LINES_MAX);
> + bitmap_from_arr64(bits, &lv->bits, GPIO_V2_LINES_MAX);
> +
> + num_set = bitmap_gather(vals, bits, mask, lr->num_lines);

It looks like GPIO_V2_LINES_MAX is always 64, and so I wonder: is
my understanding correct that all bits in ->mask and ->bits beyond
lr->num_lines are clear?

If so, you can seemingly pass the GPIO_V2_LINES_MAX instead of
lr->num_lines, and that way it will be small_cons_nbits()-optimized.

> if (num_set == 0)
> return -EINVAL;
>
> - if (num_set != 1) {
> + for_each_set_bit(i, mask, lr->num_lines) {
> + if (!test_bit(FLAG_IS_OUT, &lr->lines[i].desc->flags))
> + return -EPERM;
> + }
> +
> + if (num_set == 1) {
> + descs = &lr->lines[find_first_bit(mask, lr->num_lines)].desc;
> + } else {
> /* build compacted desc array and values */
> descs = kmalloc_array(num_set, sizeof(*descs), GFP_KERNEL);
> if (!descs)
> return -ENOMEM;
> - for (didx = 0, i = 0; i < lr->num_lines; i++) {
> - if (lv->mask & BIT_ULL(i)) {
> - descs[didx] = lr->lines[i].desc;
> - didx++;
> - }
> - }
> +
> + didx = 0;
> + for_each_set_bit(i, mask, lr->num_lines)
> + descs[didx++] = lr->lines[i].desc;
> }
> ret = gpiod_set_array_value_complex(false, true, num_set,
> descs, NULL, vals);
> --
> 2.40.0.1.gaa8946217a0b