Re: [PATCH 2/8] drm/fb-helper: Add support for DRM_FORMAT_C[124]

Thomas Zimmermann
2022-02-17T14:57:16Z

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Hi Geert

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@linux-m68k.org>
> ---
> drivers/gpu/drm/drm_fb_helper.c | 120 +++++++++++++++++++++++++-------
> 1 file changed, 93 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index ed43b987d306afce..a4afed0de1570841 100644
> --- 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.

> + case 1:
> + offset += clip->x1 / 8;
> + len = DIV_ROUND_UP(len + clip->x1 % 8, 8);
> + break;
> +

Style: no empty lines here.

> + case 2:
> + offset += clip->x1 / 4;
> + len = DIV_ROUND_UP(len + clip->x1 % 4, 4);
> + break;
> +
> + case 4:
> + offset += clip->x1 / 2;
> + len = DIV_ROUND_UP(len + clip->x1 % 2, 2);
> + break;
> +

Can we handle case C8 like C[124]? Seems cleaner to me.

> + default:
> + offset += clip->x1 * fb->format->cpp[0];
> + len *= fb->format->cpp[0];
> + break;
> + }
> +
> + src = fb_helper->fbdev->screen_buffer + offset;
> iosys_map_incr(dst, offset); /* go to first pixel within clip rect */
>
> for (y = clip->y1; y < clip->y2; y++) {
> @@ -1231,19 +1253,30 @@ static bool drm_fb_pixel_format_equal(const struct fb_var_screeninfo *var_1,
> }
>
> static void drm_fb_helper_fill_pixel_fmt(struct fb_var_screeninfo *var,
> - u8 depth)
> -{
> - switch (depth) {
> - case 8:
> + const struct drm_format_info *format)
> +{
> + u8 depth = format->depth;
> +
> + switch (format->format) {
> + // FIXME Perhaps
> + // #define DRM_FORMAT_C0 fourcc_code('C', '0', ' ', ' ')

What is C0?

> + // if ((format & fourcc_code(0xff, 0xf8, 0xff, 0xff) == DRM_FORMAT_C0) ...
> + case DRM_FORMAT_C1:
> + case DRM_FORMAT_C2:
> + case DRM_FORMAT_C4:
> + case DRM_FORMAT_C8:
> var->red.offset = 0;
> var->green.offset = 0;
> var->blue.offset = 0;
> - var->red.length = 8; /* 8bit DAC */
> - var->green.length = 8;
> - var->blue.length = 8;
> + var->red.length = depth;
> + var->green.length = depth;
> + var->blue.length = depth;
> var->transp.offset = 0;
> var->transp.length = 0;
> - break;
> + return;
> + }
> +
> + switch (depth) {
> case 15:
> var->red.offset = 10;
> var->green.offset = 5;
> @@ -1298,7 +1331,9 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> {
> struct drm_fb_helper *fb_helper = info->par;
> struct drm_framebuffer *fb = fb_helper->fb;
> + const struct drm_format_info *format = fb->format;
> struct drm_device *dev = fb_helper->dev;
> + unsigned int bpp;
>
> if (in_dbg_master())
> return -EINVAL;
> @@ -1308,22 +1343,34 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> var->pixclock = 0;
> }
>
> - if ((drm_format_info_block_width(fb->format, 0) > 1) ||
> - (drm_format_info_block_height(fb->format, 0) > 1))
> - return -EINVAL;
> + switch (format->format) {
> + case DRM_FORMAT_C1:
> + case DRM_FORMAT_C2:
> + case DRM_FORMAT_C4:
> + bpp = format->depth;
> + break;

Added C8 here would be more consistent.

> +
> + default:
> + if ((drm_format_info_block_width(format, 0) > 1) ||
> + (drm_format_info_block_height(format, 0) > 1))
> + return -EINVAL;
> +
> + bpp = format->cpp[0] * 8;
> + break;
> + }
>
> /*
> * Changes struct fb_var_screeninfo are currently not pushed back
> * to KMS, hence fail if different settings are requested.
> */
> - if (var->bits_per_pixel > fb->format->cpp[0] * 8 ||
> + if (var->bits_per_pixel > bpp ||
> var->xres > fb->width || var->yres > fb->height ||
> var->xres_virtual > fb->width || var->yres_virtual > fb->height) {
> drm_dbg_kms(dev, "fb requested width/height/bpp can't fit in current fb "
> "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n",
> var->xres, var->yres, var->bits_per_pixel,
> var->xres_virtual, var->yres_virtual,
> - fb->width, fb->height, fb->format->cpp[0] * 8);
> + fb->width, fb->height, bpp);
> return -EINVAL;
> }
>
> @@ -1338,13 +1385,13 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> !var->blue.length && !var->transp.length &&
> !var->red.msb_right && !var->green.msb_right &&
> !var->blue.msb_right && !var->transp.msb_right) {
> - drm_fb_helper_fill_pixel_fmt(var, fb->format->depth);
> + drm_fb_helper_fill_pixel_fmt(var, format);
> }
>
> /*
> * Likewise, bits_per_pixel should be rounded up to a supported value.
> */
> - var->bits_per_pixel = fb->format->cpp[0] * 8;
> + var->bits_per_pixel = bpp;
>
> /*
> * drm fbdev emulation doesn't support changing the pixel format at all,
> @@ -1680,11 +1727,20 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
> }
>
> static void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
> - uint32_t depth)
> + uint32_t format)
> {
> info->fix.type = FB_TYPE_PACKED_PIXELS;
> - info->fix.visual = depth == 8 ? FB_VISUAL_PSEUDOCOLOR :
> - FB_VISUAL_TRUECOLOR;
> + switch (format) {
> + case DRM_FORMAT_C1:
> + case DRM_FORMAT_C2:
> + case DRM_FORMAT_C4:
> + case DRM_FORMAT_C8:
> + info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
> + break;
> + default:
> + info->fix.visual = FB_VISUAL_TRUECOLOR;
> + break;
> + }
> info->fix.mmio_start = 0;
> info->fix.mmio_len = 0;
> info->fix.type_aux = 0;
> @@ -1701,19 +1757,29 @@ static void drm_fb_helper_fill_var(struct fb_info *info,
> uint32_t fb_width, uint32_t fb_height)
> {
> struct drm_framebuffer *fb = fb_helper->fb;
> + const struct drm_format_info *format = fb->format;
>
> - WARN_ON((drm_format_info_block_width(fb->format, 0) > 1) ||
> - (drm_format_info_block_height(fb->format, 0) > 1));
> info->pseudo_palette = fb_helper->pseudo_palette;
> info->var.xres_virtual = fb->width;
> info->var.yres_virtual = fb->height;
> - info->var.bits_per_pixel = fb->format->cpp[0] * 8;
> + switch (format->format) {
> + case DRM_FORMAT_C1:
> + case DRM_FORMAT_C2:
> + case DRM_FORMAT_C4:
> + info->var.bits_per_pixel = format->depth;
> + break;

C8.

The fbdev helpers look correct to me. I'm not so sure about the usage
of the format info; especially the depth field. The docs say that the
field is deprecated and should be 0. Maybe depth can be handled within
fbdev?

Best regards
Thomas

> +
> + default:
> + WARN_ON((drm_format_info_block_width(format, 0) > 1) ||
> + (drm_format_info_block_height(format, 0) > 1));
> + info->var.bits_per_pixel = format->cpp[0] * 8;
> + }
> info->var.accel_flags = FB_ACCELF_TEXT;
> info->var.xoffset = 0;
> info->var.yoffset = 0;
> info->var.activate = FB_ACTIVATE_NOW;
>
> - drm_fb_helper_fill_pixel_fmt(&info->var, fb->format->depth);
> + drm_fb_helper_fill_pixel_fmt(&info->var, format);
>
> info->var.xres = fb_width;
> info->var.yres = fb_height;
> @@ -1738,7 +1804,7 @@ void drm_fb_helper_fill_info(struct fb_info *info,
> {
> struct drm_framebuffer *fb = fb_helper->fb;
>
> - drm_fb_helper_fill_fix(info, fb->pitches[0], fb->format->depth);
> + drm_fb_helper_fill_fix(info, fb->pitches[0], fb->format->format);
> drm_fb_helper_fill_var(info, fb_helper,
> sizes->fb_width, sizes->fb_height);
>

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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