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

[Yury Norov]

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@xxxxxxxxxxxxxxx>
> ---
>  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