[PATCH 16/33] efi/gop: Allow specifying mode by x

Ard Biesheuvel
2020-04-24T13:06:53Z

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

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>
---
Documentation/fb/efifb.rst | 5 ++
drivers/firmware/efi/libstub/gop.c | 84 +++++++++++++++++++++++++++++-
2 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst
index 367fbda2f4da..635275071307 100644
--- 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 a32b784b4577..cc84e6a82f54 100644
--- 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;
}
--
2.17.1