[PATCH v1 1/2] PCI/AER: Use for_each_set_bit()

[Bjorn Helgaas]

On Tue, Aug 27, 2019 at 06:18:22PM +0300, Andy Shevchenko wrote:
> This simplifies and standardizes slot manipulation code
> by using for_each_set_bit() library function.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> ---
>  drivers/pci/pcie/aer.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index b45bc47d04fe..f883f81d759a 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -15,6 +15,7 @@
>  #define pr_fmt(fmt) "AER: " fmt
>  #define dev_fmt pr_fmt
>  
> +#include <linux/bitops.h>
>  #include <linux/cper.h>
>  #include <linux/pci.h>
>  #include <linux/pci-acpi.h>
> @@ -657,7 +658,8 @@ const struct attribute_group aer_stats_attr_group = {
>  static void pci_dev_aer_stats_incr(struct pci_dev *pdev,
>  				   struct aer_err_info *info)
>  {
> -	int status, i, max = -1;
> +	unsigned long status = info->status & ~info->mask;
> +	int i, max = -1;
>  	u64 *counter = NULL;
>  	struct aer_stats *aer_stats = pdev->aer_stats;
>  
> @@ -682,10 +684,8 @@ static void pci_dev_aer_stats_incr(struct pci_dev *pdev,
>  		break;
>  	}
>  
> -	status = (info->status & ~info->mask);
> -	for (i = 0; i < max; i++)
> -		if (status & (1 << i))
> -			counter[i]++;
> +	for_each_set_bit(i, &status, max)

I applied this, but I confess to being a little ambivalent.  It's
arguably a little easier to read, but it's not nearly as efficient
(not a great concern here) and more importantly much harder to verify
that it's correct because you have to chase through
for_each_set_bit(), find_first_bit(), _ffs(), etc, etc.  No doubt it's
great for bitmaps of arbitrary size, but for a simple 32-bit register
I'm a little hesitant.  But I applied it anyway.

> +		counter[i]++;
>  }
>  
>  static void pci_rootport_aer_stats_incr(struct pci_dev *pdev,
> @@ -717,14 +717,11 @@ static void __print_tlp_header(struct pci_dev *dev,
>  static void __aer_print_error(struct pci_dev *dev,
>  			      struct aer_err_info *info)
>  {
> -	int i, status;
> +	unsigned long status = info->status & ~info->mask;
>  	const char *errmsg = NULL;
> -	status = (info->status & ~info->mask);
> -
> -	for (i = 0; i < 32; i++) {
> -		if (!(status & (1 << i)))
> -			continue;
> +	int i;
>  
> +	for_each_set_bit(i, &status, 32) {
>  		if (info->severity == AER_CORRECTABLE)
>  			errmsg = i < ARRAY_SIZE(aer_correctable_error_string) ?
>  				aer_correctable_error_string[i] : NULL;
> -- 
> 2.23.0.rc1
>