linux-kernel - Re: [PATCH 6/7] platform/x86: fujitsu-laptop: More accurately represent the hotkey ring buffer managed by firmware

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Date:   Wed, 28 Feb 2018 18:13:55 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Michał Kępień <kernel@...pniu.pl>
Cc:     Jonathan Woithe <jwoithe@...t42.net>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] platform/x86: fujitsu-laptop: More accurately
 represent the hotkey ring buffer managed by firmware

On Tue, Feb 27, 2018 at 11:15 PM, Michał Kępień <kernel@...pniu.pl> wrote:
> The MAX_HOTKEY_RINGBUFFER_SIZE constant is set to 100, which allows up
> to 100 hotkey events to be drained from the firmware ring buffer upon
> module load.  However, no known firmware is capable of holding more than
> 16 hotkey events in its internal ring buffer:

> The RINGBUFFERSIZE constant is set to 40, which allows the module to
> queue up to 40 hotkey events for delivery to user space.  As this value
> seems arbitrarily chosen and 16 should be more than enough for any
> practical use case, merge the two aforementioned constants into one
> (HOTKEY_RINGBUFFER_SIZE) in order to simplify code and more accurately
> represent the underlying data structure.

> +#define HOTKEY_RINGBUFFER_SIZE         16

This need the comment or a

BUILD_BUG_ON(!is_power_of_2(...));


> -       ret = kfifo_alloc(&priv->fifo, RINGBUFFERSIZE * sizeof(int),
> +       ret = kfifo_alloc(&priv->fifo, HOTKEY_RINGBUFFER_SIZE * sizeof(int),
>                           GFP_KERNEL);

>         while (call_fext_func(device, FUNC_BUTTONS, OP_GET_EVENTS,
>                               0x0, 0x0) != 0 &&
> -              i++ < MAX_HOTKEY_RINGBUFFER_SIZE)
> +              i++ < HOTKEY_RINGBUFFER_SIZE)
>                 ; /* No action, result is discarded */

This looks horrible.
Can it be redone

do {
 if (call...() == 0)
  break;
} while (i++ < ...);

?

>         while ((irb = call_fext_func(device, FUNC_BUTTONS, OP_GET_EVENTS,
>                                      0x0, 0x0)) != 0 &&
> -              i++ < MAX_HOTKEY_RINGBUFFER_SIZE) {
> +              i++ < HOTKEY_RINGBUFFER_SIZE) {

Ditto.

>                 scancode = irb & 0x4ff;
>                 if (sparse_keymap_entry_from_scancode(priv->input, scancode))
>                         acpi_fujitsu_laptop_press(device, scancode);


-- 
With Best Regards,
Andy Shevchenko