[PATCH 17/33] efi/gop: Allow specifying depth as well as resolution

Ard Biesheuvel
2020-04-24T13:08:02Z

From: Arvind Sankar <nivedita@alum.mit.edu>

Extend the video mode argument to handle an optional color depth
specification of the form
video=efifb:<xres>x<yres>[-(rgb|bgr|<bpp>)]

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200320020028.1936003-14-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
Documentation/fb/efifb.rst | 8 +++--
drivers/firmware/efi/libstub/gop.c | 48 ++++++++++++++++++++++++++----
2 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst
index 635275071307..eca38466487a 100644
--- a/Documentation/fb/efifb.rst
+++ b/Documentation/fb/efifb.rst
@@ -50,9 +50,11 @@ mode=n
The EFI stub will set the mode of the display to mode number n if
possible.

-<xres>x<yres>
+<xres>x<yres>[-(rgb|bgr|<bpp>)]
The EFI stub will search for a display mode that matches the specified
- horizontal and vertical resolution, and set the mode of the display to
- it if one is found.
+ horizontal and vertical resolution, and optionally bit depth, and set
+ the mode of the display to it if one is found. The bit depth can either
+ "rgb" or "bgr" to match specifically those pixel formats, or a number
+ for a mode with matching bits per pixel.

Edgar Hucek <gimli@dark-green.com>
diff --git a/drivers/firmware/efi/libstub/gop.c b/drivers/firmware/efi/libstub/gop.c
index cc84e6a82f54..848cb605a9c4 100644
--- a/drivers/firmware/efi/libstub/gop.c
+++ b/drivers/firmware/efi/libstub/gop.c
@@ -27,6 +27,8 @@ static struct {
u32 mode;
struct {
u32 width, height;
+ int format;
+ u8 depth;
} res;
};
} cmdline __efistub_global = { .option = EFI_CMDLINE_NONE };
@@ -50,7 +52,8 @@ static bool parse_modenum(char *option, char **next)

static bool parse_res(char *option, char **next)
{
- u32 w, h;
+ u32 w, h, d = 0;
+ int pf = -1;

if (!isdigit(*option))
return false;
@@ -58,11 +61,26 @@ static bool parse_res(char *option, char **next)
if (*option++ != 'x' || !isdigit(*option))
return false;
h = simple_strtoull(option, &option, 10);
+ if (*option == '-') {
+ option++;
+ if (strstarts(option, "rgb")) {
+ option += strlen("rgb");
+ pf = PIXEL_RGB_RESERVED_8BIT_PER_COLOR;
+ } else if (strstarts(option, "bgr")) {
+ option += strlen("bgr");
+ pf = PIXEL_BGR_RESERVED_8BIT_PER_COLOR;
+ } else if (isdigit(*option))
+ d = simple_strtoull(option, &option, 10);
+ else
+ return false;
+ }
if (*option && *option++ != ',')
return false;
cmdline.option = EFI_CMDLINE_RES;
cmdline.res.width = w;
cmdline.res.height = h;
+ cmdline.res.format = pf;
+ cmdline.res.depth = d;

*next = option;
return true;
@@ -123,6 +141,18 @@ static u32 choose_mode_modenum(efi_graphics_output_protocol_t *gop)
return cmdline.mode;
}

+static u8 pixel_bpp(int pixel_format, efi_pixel_bitmask_t pixel_info)
+{
+ if (pixel_format == PIXEL_BIT_MASK) {
+ u32 mask = pixel_info.red_mask | pixel_info.green_mask |
+ pixel_info.blue_mask | pixel_info.reserved_mask;
+ if (!mask)
+ return 0;
+ return __fls(mask) - __ffs(mask) + 1;
+ } else
+ return 32;
+}
+
static u32 choose_mode_res(efi_graphics_output_protocol_t *gop)
{
efi_status_t status;
@@ -133,16 +163,21 @@ static u32 choose_mode_res(efi_graphics_output_protocol_t *gop)

u32 max_mode, cur_mode;
int pf;
+ efi_pixel_bitmask_t pi;
u32 m, w, h;

mode = efi_table_attr(gop, mode);

cur_mode = efi_table_attr(mode, mode);
info = efi_table_attr(mode, info);
- w = info->horizontal_resolution;
- h = info->vertical_resolution;
+ pf = info->pixel_format;
+ pi = info->pixel_information;
+ w = info->horizontal_resolution;
+ h = info->vertical_resolution;

- if (w == cmdline.res.width && h == cmdline.res.height)
+ if (w == cmdline.res.width && h == cmdline.res.height &&
+ (cmdline.res.format < 0 || cmdline.res.format == pf) &&
+ (!cmdline.res.depth || cmdline.res.depth == pixel_bpp(pf, pi)))
return cur_mode;

max_mode = efi_table_attr(mode, max_mode);
@@ -157,6 +192,7 @@ static u32 choose_mode_res(efi_graphics_output_protocol_t *gop)
continue;

pf = info->pixel_format;
+ pi = info->pixel_information;
w = info->horizontal_resolution;
h = info->vertical_resolution;

@@ -164,7 +200,9 @@ static u32 choose_mode_res(efi_graphics_output_protocol_t *gop)

if (pf == PIXEL_BLT_ONLY || pf >= PIXEL_FORMAT_MAX)
continue;
- if (w == cmdline.res.width && h == cmdline.res.height)
+ if (w == cmdline.res.width && h == cmdline.res.height &&
+ (cmdline.res.format < 0 || cmdline.res.format == pf) &&
+ (!cmdline.res.depth || cmdline.res.depth == pixel_bpp(pf, pi)))
return m;
}

--
2.17.1