V853SDK：奇怪的帧缓冲区操作

Alb702 LV 5

在我的系统上，在显示设置的 board.dtb 中，像素格式指定为 RGBA。每个像素都用 32 位数字进行编码。三个最低有效字节是 R/G/B 分量。最高有效字节是 Alpha 通道。 Alpha 通道应该像这样工作：
值 0xff - 像素完全透明（不可见）。
值 0 - 像素完全不透明
其他值是中等透明度。

我编写了一个测试程序，以像素为单位输出 alpha 值为 0 的图像。但是，我得到了黑屏。在进一步的实验中我我发现如果 Alpha 通道值不是零，则图像是可见的。
但 Alpha 通道值不会影响透明度级别。

这很奇怪。

我查看了linux内核中视频控制器驱动程序的源代码。发现在可选的 colorbar 函数中，在形成时绘制颜色条图像的 Alpha 通道值设置为 0xff 。也就是说，这种行为从驾驶员的角度来看，这是“正常”的。但从标准的角度来看——不。

lvgl 库很可能也考虑到了这一点，因为 lv_examples 可以正确显示图像。但其他程序要么输出扭曲的图像花或黑屏。

经过进一步调查内核驱动程序，我发现在图像层设置中对于显示引擎参数中的 RT-Mixer 块：

配置.info.alpha_mode = 0;

初始化帧缓冲区时。

该值对应于“标准”Alpha 通道操作。然而它不起作用。

这是什么？ RT-Mixer 硬件错误？或者可以通过参数值来修正吗？

我可以尝试自己解决这个问题，但是我没有V853的Display_Engine的描述，也找不到它。我在哪里可以得到它？
有来自较旧处理器的 Diplay_Engine 的描述：H3、H5、H8、A83.
也许其中一些与V853一致（RT-Mixer0 偏移地址）？

在我的设备程序中，我可以轻松设置像素的 Alpha 通道，以便我有一个图像，但我想让它按照标准工作。

awwwwa LV 7

try to use english to describe, the translate I can't understand.

Alb702 LV 5

@awwwwa

Ok.

On my system in board.dtb set display parameter "fb format" = 0 : RGBA. This format is 32 bits per pixel. Three low bytes are component R/G/B . High byte is alpha-channel. Alpha-channel must work :

value = 0xff : pixel fully transparent (invisible) .
value = 0 : pixel fully non-transparent.
intermediate values : transparency level.

I wrote simple test program, which draw image by pixels with alpha-channel value 0 (fully non-transparent), but i got a black screen. To experiment, i set pixels alpha channel to non-zero value. The image became visible, but alpha-channel value is not affect to transparency level.

This is very strange. Work of alpha-channel fully non-correct.

In kernel display driver source i found optional function "color bar", which draw color bands. In this function programmed pixels with alpha-channel value = 0xff. It mean, in this function wrong work of driver is "workarounded".

I think, this also taken into account in LVGL library in SDK : "lv_examples" application draw right images.
But other programs, built separately from SDK, draw distorted colors, or black screen.

Also i found in kernel display driver source init of parameter

config.info.alpha_mode = 0;

for RT-Mixer (part of Display Engine) layer in framebuffer initialization. This parameter value means "alpha-channel for each pixel", and i may to expect "standard" work of alpha-channel. In fact, this is not the case.

What is this? Hardware bug of RT-Mixer? or it may be corrected through RT-Mixer register values?

I may to try to correct problem myself, but i do not have documentation for V853 Display Engine.
Where i may download it?
I have description of Display Engine for old AllWinner MPUs : H3, H8, A83. What of this is match to V853 Display Engine?

I may to easy set alpha-channel of pixel to value, which work, for my programs to this device, but i need standard work of framebuffer.

awwwwa LV 7

@alb702 try to cat /sys/class/disp/disp/attr/sys

empty:

root@TinaLinux:/# cat /sys/class/disp/disp/attr/sys
screen 0:
de_rate 300000000 hz, ref_fps:62
mgr0: 800x1280 fmt[rgb] cs[0x204] range[full] eotf[0x4] bits[8bits] err[0] force_sync[0] unblank direct_show[false] iommu[1]
dmabuf: cache[0] cache max[0] umap skip[0] umap skip max[52]
        lcd output      backlight(100)  fps:62.1         800x1280
        err:0   skip:228        irq:2786        vsync:0 vsync_skip:0
   BUF    enable ch[1] lyr[0] z[16] prem[N] a[pixel 255] fmt[  0] fb[ 800,1280; 800,1280; 800,1280] crop[   0,   0, 800,1280] frame[   0,   0, 800,1280] addr[ff800000,       0,       0] flags[0x       0] trd[0,0] depth[ 0]

add layer

cat /sys/class/disp/disp/attr/sys
screen 0:
de_rate 300000000 hz, ref_fps:62
mgr0: 800x1280 fmt[rgb] cs[0x204] range[full] eotf[0x4] bits[8bits] err[0] force_sync[0] unblank direct_show[false] iommu[1]
dmabuf: cache[0] cache max[0] umap skip[0] umap skip max[52]
        lcd output      backlight(100)  fps:62.1         800x1280
        err:933 skip:228        irq:6815        vsync:0 vsync_skip:0
 COLOR    enable ch[0] lyr[0] z[16] prem[N] a[pixel   0] fmt[  0] fb[   0,   0;   0,   0;   0,   0] crop[   0,   0, 200,1280] frame[   0,   0, 200,1280] addr[ffff0000,       0,       0] flags[0x       0] trd[0,0]
depth[ 0]  COLOR    enable ch[0] lyr[1] z[16] prem[N] a[pixel   0] fmt[  0] fb[   0,   0;   0,   0;   0,   0] crop[ 200,   0, 200,1280] frame[ 200,   0, 200,1280] addr[ff00ff00,       0,       0] flags[0x       0] trd[0,0]
depth[ 0]  COLOR    enable ch[0] lyr[2] z[16] prem[N] a[pixel   0] fmt[  0] fb[   0,   0;   0,   0;   0,   0] crop[ 400,   0, 200,1280] frame[ 400,   0, 200,1280] addr[ff0000ff,       0,       0] flags[0x       0] trd[0,0]
depth[ 0]  COLOR    enable ch[0] lyr[3] z[16] prem[N] a[pixel   0] fmt[  0] fb[   0,   0;   0,   0;   0,   0] crop[ 600,   0, 200,1280] frame[ 600,   0, 200,1280] addr[ffffff00,       0,       0] flags[0x       0] trd[0,0]
depth[ 0]    BUF    enable ch[1] lyr[0] z[16] prem[N] a[pixel 255] fmt[  0] fb[ 800,1280; 800,1280; 800,1280] crop[   0,   0, 800,1280] frame[   0,   0, 800,1280] addr[ff800000,       0,       0] flags[0x       0] trd[0,0]
depth[ 0]

Alb702 LV 5

@awwwwa 在 V853SDK：奇怪的帧缓冲区操作中说：

cat /sys/class/disp/disp/attr/sys

cat /sys/class/disp/disp/attr/sys
screen 0:
de_rate 300000000 hz, ref_fps:60
mgr0: 1920x1080 fmt[rgb] cs[0x204] range[full] eotf[0x4] bits[8bits] err[3] force_sync[0] unblank direct_show[false] iommu[1]
dmabuf: cache[0] cache max[0] umap skip[0] umap skip max[52]
	lcd output	backlight(150)	fps:59.5	1920x1080
	err:0	skip:154	irq:8267	vsync:0	vsync_skip:0	
   BUF    enable ch[1] lyr[0] z[16] prem[N] a[pixel 255] fmt[  0] fb[1920,1080;1920,1080;1920,1080] crop[   0,   0,1920,1080] frame[   0,   0,1920,1080] addr[48400000,       0,       0] flags[0x       0] trd[0,0]
depth[ 0]

"add layer" - i do not understanded.

awwwwa LV 7

@alb702 add your layer and cat that file see what layer you configured