Hi Thomas,
On Fri, Feb 18, 2022 at 9:14 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
Am 17.02.22 um 17:12 schrieb Geert Uytterhoeven:
On Thu, Feb 17, 2022 at 3:57 PM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
Am 15.02.22 um 17:52 schrieb Geert Uytterhoeven:
Add support for color-indexed frame buffer formats with two, four, and
sixteen colors to the DRM framebuffer helper functions:
1. Add support for depths 1/2/4 to the damage helper,
2. For color-indexed modes, the length of the color bitfields must be
set to the color depth, else the logo code may pick a logo with too
many colors. Drop the incorrect DAC width comment, which
originates from the i915 driver.
3. Accept C[124] modes when validating or filling in struct
fb_var_screeninfo, and use the correct number of bits per pixel.
4. Set the visual to FB_VISUAL_PSEUDOCOLOR for all supported
color-indexed modes.
Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -376,12 +376,34 @@ static void drm_fb_helper_damage_blit_real(struct drm_fb_helper *fb_helper,
struct iosys_map *dst)
{
struct drm_framebuffer *fb = fb_helper->fb;
- unsigned int cpp = fb->format->cpp[0];
- size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;
- void *src = fb_helper->fbdev->screen_buffer + offset;
- size_t len = (clip->x2 - clip->x1) * cpp;
+ size_t offset = clip->y1 * fb->pitches[0];
+ size_t len = clip->x2 - clip->x1;
unsigned int y;
+ void *src;
+ switch (fb->format->depth) {
The depth field is deprecated. It's probably better to use
fb->format->format and test against 4CC codes.
The reason I checked for depth instead of a 4CC code is that the only
thing that matters here is the number of bits per pixel. Hence this
function won't need any changes to support R1, R2, R4, and D1 later.
When we get here, we already know that we are using a format that
is supported by the fbdev helper code, and thus passed the 4CC
checks elsewhere.
At some point, we will probably have to change several of these tests to
4cc. C8 and RGB332 both have 8-bit depth/bpp; same for C4 and RGB121; or
whatever low-color formats we also want to add.
It's not a blocker now, but maybe something to keep in mind.
Alternatively, we could introduce drm_format_info_bpp() earlier in
the series, and use that?
Having a helper for this might indeed be useful. We use depth for the
number of color bits and bpp for the number of bits in he pixel. That's
important for XRGB8888, where depth is 24, or XRGB555 where depth is 15.
If that makes sense, maybe have a helper for depth and one for bpp, even
if they return the same value in most of the cases.
The helper for bpp is introduced in "[PATCH 3/8] drm/fourcc: Add
drm_format_info_bpp() helper".
I don't think we need a helper for depth, there's already the .depth
field. It might be deprecated, but it's still used?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
