Re: [igt-dev] [PATCH i-g-t v3 1/3] tests/kms_writeback: Use endianness accessor to fill pixels

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Fri, 10 Jun 2022 14:16:45 +0200
Maxime Ripard <maxime@cerno.tech> wrote:

> The fill_fb() function in the kms_writeback test suite will fill an
> XRGB8888 buffer using a pattern passed an an argument. However, the
> pattern is native endian, while XRGB8888 is little-endian.
> 
> Add an accessor and use it to fill the framebuffer with our pattern.
> 
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
>  lib/igt_core.h        | 9 +++++++++
>  tests/kms_writeback.c | 2 +-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/igt_core.h b/lib/igt_core.h
> index 526282faff24..aa98e8ed8deb 100644
> --- a/lib/igt_core.h
> +++ b/lib/igt_core.h
> @@ -31,6 +31,7 @@
>  #define IGT_CORE_H
>  
>  #include <assert.h>
> +#include <byteswap.h>
>  #include <setjmp.h>
>  #include <stdbool.h>
>  #include <stdint.h>
> @@ -1447,6 +1448,14 @@ void igt_kmsg(const char *format, ...);
>  #define READ_ONCE(x) (*(volatile typeof(x) *)(&(x)))
>  #define WRITE_ONCE(x, v) do *(volatile typeof(x) *)(&(x)) = (v); while (0)
>  
> +#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> +#define cpu_to_le32(x)  bswap_32(x)
> +#define le32_to_cpu(x)  bswap_32(x)
> +#else
> +#define cpu_to_le32(x)  (x)
> +#define le32_to_cpu(x)  (x)
> +#endif
> +

The explanation makes sense and these macros look right.

>  #define MSEC_PER_SEC (1000)
>  #define USEC_PER_SEC (1000*MSEC_PER_SEC)
>  #define NSEC_PER_SEC (1000*USEC_PER_SEC)
> diff --git a/tests/kms_writeback.c b/tests/kms_writeback.c
> index 6efc72df4327..cf70a28e7d56 100644
> --- a/tests/kms_writeback.c
> +++ b/tests/kms_writeback.c
> @@ -244,7 +244,7 @@ static void fill_fb(igt_fb_t *fb, uint32_t pixel)
>  
>  	pixel_count = fb->strides[0] * fb->height / sizeof(uint32_t);
>  	for (i = 0; i < pixel_count; i++)
> -		ptr[i] = pixel;
> +		ptr[i] = cpu_to_le32(pixel);
>  
>  	igt_fb_unmap_buffer(fb, ptr);
>  }

There just isn't enough context in this patch to see if this is
correct, but at least it matches the commit message.

Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>


Thanks,
pq

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