Re: [PATCH 10/11] treewide: Manually convert custom kernel_param_ops .get callbacks

[Jani Nikula]

On Thu, 21 May 2026, Kees Cook <k...@kernel.org> wrote:
> diff --git a/drivers/gpu/drm/i915/i915_mitigations.c 
> b/drivers/gpu/drm/i915/i915_mitigations.c
> index 6061eae84e9c..99cb38f355b6 100644
> --- a/drivers/gpu/drm/i915/i915_mitigations.c
> +++ b/drivers/gpu/drm/i915/i915_mitigations.c
> @@ -95,33 +95,37 @@ static int mitigations_set(const char *val, const struct 
> kernel_param *kp)
>       return 0;
>  }
>  
> -static int mitigations_get(char *buffer, const struct kernel_param *kp)
> +static int mitigations_get(struct seq_buf *buffer,
> +                        const struct kernel_param *kp)
>  {
>       unsigned long local = READ_ONCE(mitigations);
> -     int count, i;
>       bool enable;
> +     int i;

I'm fine with what you have, and I can do these as a follow-up later if
it's too much trouble, but I suggest something like this:

        const char *sep = "";

>  
> -     if (!local)
> -             return scnprintf(buffer, PAGE_SIZE, "%s\n", "off");
> +     if (!local) {
> +             seq_buf_printf(buffer, "%s\n", "off");
> +             return 0;
> +     }
>  
>       if (local & BIT(BITS_PER_LONG - 1)) {
> -             count = scnprintf(buffer, PAGE_SIZE, "%s,", "auto");
> +             seq_buf_printf(buffer, "%s,", "auto");

                seq_buf_printf(buffer, "%s%s", sep, "auto");
                sep = ",";

(In the printf the sep is just for future expansion, though I don't
expect one.)

>               enable = false;
>       } else {
>               enable = true;
> -             count = 0;
>       }
>  
>       for (i = 0; i < ARRAY_SIZE(names); i++) {
>               if ((local & BIT(i)) != enable)
>                       continue;
> -
> -             count += scnprintf(buffer + count, PAGE_SIZE - count,
> -                                "%s%s,", enable ? "" : "!", names[i]);
> +             seq_buf_printf(buffer, "%s%s,", enable ? "" : "!", names[i]);

                seq_buf_printf(buffer, "%s%s%s", sep, enable ? "" : "!", 
names[i]);
                sep = ",";

>       }

        seq_buf_puts(buffer, "\n");

>  
> -     buffer[count - 1] = '\n';
> -     return count;
> +     /* Replace the trailing comma with a newline. */
> +     if (!seq_buf_has_overflowed(buffer) && buffer->len > 0 &&
> +         buffer->buffer[buffer->len - 1] == ',')
> +             buffer->buffer[buffer->len - 1] = '\n';

Drop the above.

I.e. keep track of sep while printing to avoid removing it later.

BR,
Jani.

> +
> +     return 0;
>  }
>  
>  static DEFINE_KERNEL_PARAM_OPS(ops, mitigations_set, mitigations_get);

-- 
Jani Nikula, Intel