efi/gop: Allow specifying depth as well as resolution

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>

diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst
index 6352750..eca3846 100644 (file)
--- 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 cc84e6a..848cb60 100644 (file)
--- 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;
        }