[PATCH 18/33] efi/gop: Allow automatically choosing the best mode

Ard Biesheuvel
2020-04-24T13:06:55Z

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

Add the ability to automatically pick the highest resolution video mode
(defined as the product of vertical and horizontal resolution) by using
a command-line argument of the form
video=efifb:auto

If there are multiple modes with the highest resolution, pick one with
the highest color depth.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200328160601.378299-2-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
Documentation/fb/efifb.rst | 6 +++
drivers/firmware/efi/libstub/gop.c | 84 +++++++++++++++++++++++++++++-
2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst
index eca38466487a..519550517fd4 100644
--- a/Documentation/fb/efifb.rst
+++ b/Documentation/fb/efifb.rst
@@ -57,4 +57,10 @@ mode=n
"rgb" or "bgr" to match specifically those pixel formats, or a number
for a mode with matching bits per pixel.

+auto
+ The EFI stub will choose the mode with the highest resolution (product
+ of horizontal and vertical resolution). If there are multiple modes
+ with the highest resolution, it will choose one with the highest color
+ depth.
+
Edgar Hucek <gimli@dark-green.com>
diff --git a/drivers/firmware/efi/libstub/gop.c b/drivers/firmware/efi/libstub/gop.c
index 848cb605a9c4..fa05a0b0adfd 100644
--- a/drivers/firmware/efi/libstub/gop.c
+++ b/drivers/firmware/efi/libstub/gop.c
@@ -18,7 +18,8 @@
enum efi_cmdline_option {
EFI_CMDLINE_NONE,
EFI_CMDLINE_MODE_NUM,
- EFI_CMDLINE_RES
+ EFI_CMDLINE_RES,
+ EFI_CMDLINE_AUTO
};

static struct {
@@ -86,6 +87,19 @@ static bool parse_res(char *option, char **next)
return true;
}

+static bool parse_auto(char *option, char **next)
+{
+ if (!strstarts(option, "auto"))
+ return false;
+ option += strlen("auto");
+ if (*option && *option++ != ',')
+ return false;
+ cmdline.option = EFI_CMDLINE_AUTO;
+
+ *next = option;
+ return true;
+}
+
void efi_parse_option_graphics(char *option)
{
while (*option) {
@@ -93,6 +107,8 @@ void efi_parse_option_graphics(char *option)
continue;
if (parse_res(option, &option))
continue;
+ if (parse_auto(option, &option))
+ continue;

while (*option && *option++ != ',')
;
@@ -211,6 +227,69 @@ static u32 choose_mode_res(efi_graphics_output_protocol_t *gop)
return cur_mode;
}

+static u32 choose_mode_auto(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, best_mode, area;
+ u8 depth;
+ int pf;
+ efi_pixel_bitmask_t pi;
+ u32 m, w, h, a;
+ u8 d;
+
+ mode = efi_table_attr(gop, mode);
+
+ cur_mode = efi_table_attr(mode, mode);
+ max_mode = efi_table_attr(mode, max_mode);
+
+ info = efi_table_attr(mode, info);
+
+ pf = info->pixel_format;
+ pi = info->pixel_information;
+ w = info->horizontal_resolution;
+ h = info->vertical_resolution;
+
+ best_mode = cur_mode;
+ area = w * h;
+ depth = pixel_bpp(pf, pi);
+
+ 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;
+ pi = info->pixel_information;
+ w = info->horizontal_resolution;
+ h = info->vertical_resolution;
+
+ efi_bs_call(free_pool, info);
+
+ if (pf == PIXEL_BLT_ONLY || pf >= PIXEL_FORMAT_MAX)
+ continue;
+ a = w * h;
+ if (a < area)
+ continue;
+ d = pixel_bpp(pf, pi);
+ if (a > area || d > depth) {
+ best_mode = m;
+ area = a;
+ depth = d;
+ }
+ }
+
+ return best_mode;
+}
+
static void set_mode(efi_graphics_output_protocol_t *gop)
{
efi_graphics_output_protocol_mode_t *mode;
@@ -223,6 +302,9 @@ static void set_mode(efi_graphics_output_protocol_t *gop)
case EFI_CMDLINE_RES:
new_mode = choose_mode_res(gop);
break;
+ case EFI_CMDLINE_AUTO:
+ new_mode = choose_mode_auto(gop);
+ break;
default:
return;
}
--
2.17.1