vrmay23 commented on code in PR #18301:
URL: https://github.com/apache/nuttx/pull/18301#discussion_r2755875716
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drivers/lcd/Kconfig:
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@@ -827,6 +827,14 @@ config LCD_ST7789_DATA_ENDIAN_LITTLE
endif # LCD_ST7789
+config LCD_ST7796
+ bool "ST7796 LCD Display"
+ default n
+ depends on SPI
+ select LCD_FRAMEBUFFER
Review Comment:
This driver requires framebuffer infrastructure to work. Maybe I have
understood wrongly. But what I have understood is that Nuttx works as an 'xor'
approach for LCD and FB drivers. The signature functions are incompatibles,
right?
This is correct because the driver allocates framebuffer: kmm_zalloc(xres *
yres * bpp); Also we are using
fb_vtable_s interface and implementing "updatearea()" not putrun(). Finally,
the driver returns at struct fb_vtable_s* rather struct lcd_dev_s*. not
/****************************************************************************
* Name: st7796_fbinitialize
*
* Description:
* Initialize the ST7796 LCD controller and framebuffer driver. This
* function allocates the framebuffer memory, initializes the driver
* structure, sends the display initialization sequence, and returns
* a pointer to the framebuffer virtual table for use with the NuttX
* framebuffer interface.
*
* Input Parameters:
* spi - Reference to the SPI driver structure to use for communication
* config - Board-specific configuration (frequency, resolution, etc.)
*
* Returned Value:
* On success, a pointer to the framebuffer virtual table is returned.
* On failure, NULL is returned.
*
****************************************************************************/
FAR struct fb_vtable_s *st7796_fbinitialize(FAR struct spi_dev_s *spi,
FAR const struct st7796_config_s
*config)
{
This driver also uses the fb.h interfaces, examples:
#include <nuttx/video/fb.h>
struct fb_videoinfo_s
struct fb_planeinfo_s
struct fb_area_s
And such thing just can be used once the symbol "CONFIG_VIDEO_FB" is enabled
via menuconfig.
Finally, the ddriver implements the framebuffer driver (not the lcd one):
priv->vtable.getvideoinfo = st7796_getvideoinfo; // fb interface
priv->vtable.getplaneinfo = st7796_getplaneinfo; // fb interface
priv->vtable.updatearea = st7796_updatearea; // fb interface
priv->vtable.ioctl = st7796_ioctl; // fb interface
So, in the end the ST7789 CAN work without a FB but ST7796 CAN NOT. This is
an architecture decision. Hence, we must enable this symbol to use it. Did you
understand my points?
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