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firmware: sysfb: Move bpp-depth calculation into screen_info helper

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Move the calculation of the bits per pixels for screen_info into a
helper function. This will make it available to other callers besides
the firmware code.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250401094056.32904-14-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2025-04-01 11:37:16 +02:00
parent e7f435b3dc
commit 1ce4c3aeef
3 changed files with 39 additions and 30 deletions
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31
drivers/firmware/sysfb_simplefb.c
View File

@ -35,36 +35,7 @@ __init bool sysfb_parse_mode(const struct screen_info *si,
if (type != VIDEO_TYPE_VLFB && type != VIDEO_TYPE_EFI)
return false;
/*
* The meaning of depth and bpp for direct-color formats is
* inconsistent:
*
* - DRM format info specifies depth as the number of color
* bits; including alpha, but not including filler bits.
* - Linux' EFI platform code computes lfb_depth from the
* individual color channels, including the reserved bits.
* - VBE 1.1 defines lfb_depth for XRGB1555 as 16, but later
* versions use 15.
* - On the kernel command line, 'bpp' of 32 is usually
* XRGB8888 including the filler bits, but 15 is XRGB1555
* not including the filler bit.
*
* It's not easily possible to fix this in struct screen_info,
* as this could break UAPI. The best solution is to compute
* bits_per_pixel from the color bits, reserved bits and
* reported lfb_depth, whichever is highest. In the loop below,
* ignore simplefb formats with alpha bits, as EFI and VESA
* don't specify alpha channels.
*/
if (si->lfb_depth > 8) {
bits_per_pixel = max(max3(si->red_size + si->red_pos,
si->green_size + si->green_pos,
si->blue_size + si->blue_pos),
si->rsvd_size + si->rsvd_pos);
bits_per_pixel = max_t(u32, bits_per_pixel, si->lfb_depth);
} else {
bits_per_pixel = si->lfb_depth;
}
bits_per_pixel = __screen_info_lfb_bits_per_pixel(si);
for (i = 0; i < ARRAY_SIZE(formats); ++i) {
const struct simplefb_format *f = &formats[i];

36
drivers/video/screen_info_generic.c
View File

@ -144,3 +144,39 @@ ssize_t screen_info_resources(const struct screen_info *si, struct resource *r,
return pos - r;
}
EXPORT_SYMBOL(screen_info_resources);
/*
* The meaning of depth and bpp for direct-color formats is
* inconsistent:
*
* - DRM format info specifies depth as the number of color
* bits; including alpha, but not including filler bits.
* - Linux' EFI platform code computes lfb_depth from the
* individual color channels, including the reserved bits.
* - VBE 1.1 defines lfb_depth for XRGB1555 as 16, but later
* versions use 15.
* - On the kernel command line, 'bpp' of 32 is usually
* XRGB8888 including the filler bits, but 15 is XRGB1555
* not including the filler bit.
*
* It is not easily possible to fix this in struct screen_info,
* as this could break UAPI. The best solution is to compute
* bits_per_pixel from the color bits, reserved bits and
* reported lfb_depth, whichever is highest.
*/
u32 __screen_info_lfb_bits_per_pixel(const struct screen_info *si)
{
u32 bits_per_pixel = si->lfb_depth;
if (bits_per_pixel > 8) {
bits_per_pixel = max(max3(si->red_size + si->red_pos,
si->green_size + si->green_pos,
si->blue_size + si->blue_pos),
si->rsvd_size + si->rsvd_pos);
bits_per_pixel = max_t(u32, bits_per_pixel, si->lfb_depth);
}
return bits_per_pixel;
}
EXPORT_SYMBOL(__screen_info_lfb_bits_per_pixel);

2
include/linux/screen_info.h
View File

@ -128,6 +128,8 @@ static inline unsigned int screen_info_video_type(const struct screen_info *si)
ssize_t screen_info_resources(const struct screen_info *si, struct resource *r, size_t num);
u32 __screen_info_lfb_bits_per_pixel(const struct screen_info *si);
#if defined(CONFIG_PCI)
void screen_info_apply_fixups(void);
struct pci_dev *screen_info_pci_dev(const struct screen_info *si);