lkml.org 
[lkml]   [2022]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
SubjectRe: [PATCH v2 1/4] drm/format-helper: Add drm_fb_{xrgb8888,gray8}_to_mono_reversed()
From
Hi

Am 04.02.22 um 14:43 schrieb Javier Martinez Canillas:
> Add support to convert XR24 and 8-bit grayscale to reversed monochrome for
> drivers that control monochromatic panels, that only have 1 bit per pixel.
>
> The drm_fb_gray8_to_mono_reversed() helper was based on the function that
> does the same in the drivers/gpu/drm/tiny/repaper.c driver.
>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
>
> (no changes since v1)
>
> drivers/gpu/drm/drm_format_helper.c | 80 +++++++++++++++++++++++++++++
> include/drm/drm_format_helper.h | 7 +++
> 2 files changed, 87 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> index 0f28dd2bdd72..cdce4b7c25d9 100644
> --- a/drivers/gpu/drm/drm_format_helper.c
> +++ b/drivers/gpu/drm/drm_format_helper.c
> @@ -584,3 +584,83 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
> return -EINVAL;
> }
> EXPORT_SYMBOL(drm_fb_blit_toio);
> +
> +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels)
> +{
> + unsigned int xb, i;
> +
> + for (xb = 0; xb < pixels / 8; xb++) {

In practice, all mode widths are multiples of 8 because VGA mandated it.
So it's ok-ish to assume this here. You should probably at least print a
warning somewhere if (pixels % 8 != 0)


> + u8 byte = 0x00;
> +
> + for (i = 0; i < 8; i++) {
> + int x = xb * 8 + i;
> +
> + byte >>= 1;
> + if (src[x] >> 7)
> + byte |= BIT(7);
> + }
> + *dst++ = byte;
> + }
> +}
> +
> +/**
> + * drm_fb_gray8_to_mono_reversed - Convert grayscale to reversed monochrome
> + * @dst: reversed monochrome destination buffer
> + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
> + * @src: 8-bit grayscale source buffer
> + * @clip: Clip rectangle area to copy
> + *
> + * DRM doesn't have native monochrome or grayscale support.
> + * Such drivers can announce the commonly supported XR24 format to userspace
> + * and use drm_fb_xrgb8888_to_gray8() to convert to grayscale and then this
> + * helper function to convert to the native format.
> + */
> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> + const struct drm_rect *clip)

There's a bug here. You want to pass in a drm_framebuffer as fourth
argument.

> +{
> +
> + size_t height = drm_rect_height(clip);
> + size_t width = drm_rect_width(clip);
> + unsigned int y;
> + const u8 *gray8 = src;
> + u8 *mono = dst;
> +
> + if (!dst_pitch)
> + dst_pitch = width;

The dst_pitch is given in bytes. You have to device by 8. Here would be
a good place to warn if (width % 8 != 0).

> +
> + for (y = 0; y < height; y++) {
> + drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch);
> + mono += (dst_pitch / 8);

The dst_pitch is already given in bytes.

> + gray8 += dst_pitch;

'gray8 += fb->pitches[0]' would be correct.

> + }
> +}
> +
> +/**
> + * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed monochrome
> + * @dst: reversed monochrome destination buffer
> + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
> + * @src: XRGB8888 source buffer
> + * @fb: DRM framebuffer
> + * @clip: Clip rectangle area to copy
> + *
> + * DRM doesn't have native monochrome support.
> + * Such drivers can announce the commonly supported XR24 format to userspace
> + * and use this function to convert to the native format.
> + *
> + * This function uses drm_fb_xrgb8888_to_gray8() to convert to grayscale and
> + * then the result is converted from grayscale to reversed monohrome.
> + */
> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> + const struct drm_framebuffer *fb,
> + const struct drm_rect *clip)
> +{
> + if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))
> + return;
> +
> + if (!dst_pitch)
> + dst_pitch = drm_rect_width(clip);
> +
> + drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip);
> + drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip);

Converting from dst into dst can give incorrect results. At some point
we probably want to add restrict qualifiers to these pointers, to help
the compiler with optimizing.

A better approach here is to pull the per-line conversion from
drm_fb_xrgb8888_to_gray8() into a separate helper and implement a
line-by-line conversion here. something like this:

drm_fb_xrgb8888_to_mono_reversed()
{
char *tmp = kmalloc(size of a single line of gray8)

for (heigth) {
drm_fb_xrgb8888_to_gray8_line(tmp, ..., src, ...);
drm_fb_gray8_to_mono_reversed(dst, ..., tmp, ...);

src += fb->pitches[0]
dst += dst_pitch;
}

kfree(tmp);
}

Best regards
Thomas

> +}
> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed);
> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
> index b30ed5de0a33..85e551a5cbe6 100644
> --- a/include/drm/drm_format_helper.h
> +++ b/include/drm/drm_format_helper.h
> @@ -43,4 +43,11 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
> const void *vmap, const struct drm_framebuffer *fb,
> const struct drm_rect *rect);
>
> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> + const struct drm_rect *clip);
> +
> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *src,
> + const struct drm_framebuffer *fb,
> + const struct drm_rect *clip);
> +
> #endif /* __LINUX_DRM_FORMAT_HELPER_H */

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2022-02-04 16:53    [W:0.770 / U:0.572 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site