efi/gop: Allow specifying mode by <xres>x<yres>

Add the ability to choose a video mode using a command-line argument of
the form
	video=efifb:<xres>x<yres>

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200320020028.1936003-13-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 367fbda..6352750 100644 (file)
--- a/Documentation/fb/efifb.rst
+++ b/Documentation/fb/efifb.rst
@@ -50,4 +50,9 @@ mode=n
         The EFI stub will set the mode of the display to mode number n if
         possible.
 
+<xres>x<yres>
+        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.
+
 Edgar Hucek <gimli@dark-green.com>

diff --git a/drivers/firmware/efi/libstub/gop.c b/drivers/firmware/efi/libstub/gop.c
index a32b784..cc84e6a 100644 (file)
--- a/drivers/firmware/efi/libstub/gop.c
+++ b/drivers/firmware/efi/libstub/gop.c
@@ -6,6 +6,7 @@
  * ----------------------------------------------------------------------- */
 
 #include <linux/bitops.h>
+#include <linux/ctype.h>
 #include <linux/efi.h>
 #include <linux/screen_info.h>
 #include <linux/string.h>
@@ -17,11 +18,17 @@
 enum efi_cmdline_option {
        EFI_CMDLINE_NONE,
        EFI_CMDLINE_MODE_NUM,
+       EFI_CMDLINE_RES
 };
 
 static struct {
        enum efi_cmdline_option option;
-       u32 mode;
+       union {
+               u32 mode;
+               struct {
+                       u32 width, height;
+               } res;
+       };
 } cmdline __efistub_global = { .option = EFI_CMDLINE_NONE };
 
 static bool parse_modenum(char *option, char **next)
@@ -41,11 +48,33 @@ static bool parse_modenum(char *option, char **next)
        return true;
 }
 
+static bool parse_res(char *option, char **next)
+{
+       u32 w, h;
+
+       if (!isdigit(*option))
+               return false;
+       w = simple_strtoull(option, &option, 10);
+       if (*option++ != 'x' || !isdigit(*option))
+               return false;
+       h = simple_strtoull(option, &option, 10);
+       if (*option && *option++ != ',')
+               return false;
+       cmdline.option     = EFI_CMDLINE_RES;
+       cmdline.res.width  = w;
+       cmdline.res.height = h;
+
+       *next = option;
+       return true;
+}
+
 void efi_parse_option_graphics(char *option)
 {
        while (*option) {
                if (parse_modenum(option, &option))
                        continue;
+               if (parse_res(option, &option))
+                       continue;
 
                while (*option && *option++ != ',')
                        ;
@@ -94,6 +123,56 @@ static u32 choose_mode_modenum(efi_graphics_output_protocol_t *gop)
        return cmdline.mode;
 }
 
+static u32 choose_mode_res(efi_graphics_output_protocol_t *gop)
+{
+       efi_status_t status;
+
+       efi_graphics_output_protocol_mode_t *mode;
+       efi_graphics_output_mode_info_t *info;
+       unsigned long info_size;
+
+       u32 max_mode, cur_mode;
+       int pf;
+       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;
+
+       if (w == cmdline.res.width && h == cmdline.res.height)
+               return cur_mode;
+
+       max_mode = efi_table_attr(mode, max_mode);
+
+       for (m = 0; m < max_mode; m++) {
+               if (m == cur_mode)
+                       continue;
+
+               status = efi_call_proto(gop, query_mode, m,
+                                       &info_size, &info);
+               if (status != EFI_SUCCESS)
+                       continue;
+
+               pf = info->pixel_format;
+               w  = info->horizontal_resolution;
+               h  = info->vertical_resolution;
+
+               efi_bs_call(free_pool, info);
+
+               if (pf == PIXEL_BLT_ONLY || pf >= PIXEL_FORMAT_MAX)
+                       continue;
+               if (w == cmdline.res.width && h == cmdline.res.height)
+                       return m;
+       }
+
+       efi_printk("Couldn't find requested mode\n");
+
+       return cur_mode;
+}
+
 static void set_mode(efi_graphics_output_protocol_t *gop)
 {
        efi_graphics_output_protocol_mode_t *mode;
@@ -103,6 +182,9 @@ static void set_mode(efi_graphics_output_protocol_t *gop)
        case EFI_CMDLINE_MODE_NUM:
                new_mode = choose_mode_modenum(gop);
                break;
+       case EFI_CMDLINE_RES:
+               new_mode = choose_mode_res(gop);
+               break;
        default:
                return;
        }