fbtft module fails to build under armv6h (but works on i686)

[dreamlocked]

Dear fellow archers,

I am writing a PKGBUILD for a driver for small TFT displays (https://github.com/notro/fbtft/wiki). The purpose is to build the individual modules without having to re-build the entire kernel.
I have drawn inspiration from other PKGBUILDS and from https://www.kernel.org/doc/Documentatio ... odules.txt
So far, the PKGBUILD works fine when built on i686, but fails on my Raspberry-pi (armv6h). The error issued by makepkg is also included below.

I have attempted the build against the raspberrypi kernel and headers version 3.10.38-1 and 3.14.2, and tried on a fresh install, with the same error.

I have a hunch that there is something missing in the linux-raspberrypi-headers package, but I may be missing something myself, as I am quite new to building individual kernel modules.

Would anyone have any insights on the conundrum?

Thank you for your time,
- dreamlocked

PKGBUILD:
$this->bbcode_second_pass_code('', '
pkgname=fbtft-git
pkgver=r226.24cf1c1
pkgrel=1
pkgdesc="Linux Framebuffer drivers for small TFT LCD display modules"
arch=('armv6h')
url="https://github.com/notro/fbtft"
license=('GPL')
depends=()
makedepends=('git' 'linux-raspberrypi-headers')
source=("$pkgname"::'git+https://github.com/notro/fbtft.git')
md5sums=('SKIP')

pkgver() {
cd "${srcdir}/${pkgname}"
printf "r%s.%s" "$(git rev-list --count HEAD)" "$(git rev-parse --short HEAD)"
}

build() {
cd "${srcdir}/${pkgname}"

make -C /lib/modules/`uname -r`/build M=${PWD} \
CONFIG_FB_TFT=m \
CONFIG_FB_TFT_HX8340BN=n \
CONFIG_FB_TFT_HX8347D=n \
CONFIG_FB_TFT_HX8353D=n \
CONFIG_FB_TFT_ILI9320=n \
CONFIG_FB_TFT_ILI9325=n \
CONFIG_FB_TFT_ILI9340=n \
CONFIG_FB_TFT_ILI9341=n \
CONFIG_FB_TFT_PCD8544=n \
CONFIG_FB_TFT_S6D1121=n \
CONFIG_FB_TFT_SSD1289=n \
CONFIG_FB_TFT_SSD1306=n \
CONFIG_FB_TFT_SSD1331=n \
CONFIG_FB_TFT_SSD1351=n \
CONFIG_FB_TFT_ST7735R=m \
CONFIG_FB_TFT_TINYLCD=n \
CONFIG_FB_TFT_WATTEROTT=n \
CONFIG_FB_FLEX=n \
CONFIG_FB_TFT_FBTFT_DEVICE=m \
modules

}
package() {
cd "${srcdir}/${pkgname}"
make -C /lib/modules/`uname -r`/build M=${PWD} INSTALL_MOD_PATH=${pkgdir}/usr modules_install
}
')

make / makepkg error:
$this->bbcode_second_pass_code('', '
==> Starting build()...
make: Entering directory '/usr/src/linux-3.10.38-1-ARCH'
CC [M] ~/fbtft/src/fbtft-git/fbtft-core.o
~/fbtft/src/fbtft-git/fbtft-core.c: In function 'fbtft_unregister_backlight':
~/fbtft/src/fbtft-git/fbtft-core.c:231:15: error: 'struct fb_info' has no member named 'bl_dev'
if (par->info->bl_dev) {
^
~/fbtft/src/fbtft-git/fbtft-core.c:232:12: error: 'struct fb_info' has no member named 'bl_dev'
par->info->bl_dev->props.power = FB_BLANK_POWERDOWN;
^
~/fbtft/src/fbtft-git/fbtft-core.c:233:36: error: 'struct fb_info' has no member named 'bl_dev'
backlight_update_status(par->info->bl_dev);
^
~/fbtft/src/fbtft-git/fbtft-core.c:234:21: error: 'struct fb_info' has no member named 'bl_dev'
bl_ops = par->info->bl_dev->ops;
^
~/fbtft/src/fbtft-git/fbtft-core.c:235:40: error: 'struct fb_info' has no member named 'bl_dev'
backlight_device_unregister(par->info->bl_dev);
^
~/fbtft/src/fbtft-git/fbtft-core.c:236:12: error: 'struct fb_info' has no member named 'bl_dev'
par->info->bl_dev = NULL;
^
~/fbtft/src/fbtft-git/fbtft-core.c: In function 'fbtft_register_backlight':
~/fbtft/src/fbtft-git/fbtft-core.c:280:11: error: 'struct fb_info' has no member named 'bl_dev'
par->info->bl_dev = bd;
^
~/fbtft/src/fbtft-git/fbtft-core.c: In function 'fbtft_register_framebuffer':
~/fbtft/src/fbtft-git/fbtft-core.c:961:13: error: 'struct fb_info' has no member named 'bl_dev'
if (fb_info->bl_dev) {
^
~/fbtft/src/fbtft-git/fbtft-core.c:962:10: error: 'struct fb_info' has no member named 'bl_dev'
fb_info->bl_dev->props.power = FB_BLANK_UNBLANK;
^
~/fbtft/src/fbtft-git/fbtft-core.c:963:10: error: 'struct fb_info' has no member named 'bl_dev'
fb_info->bl_dev->ops->update_status(fb_info->bl_dev);
^
~/fbtft/src/fbtft-git/fbtft-core.c:963:46: error: 'struct fb_info' has no member named 'bl_dev'
fb_info->bl_dev->ops->update_status(fb_info->bl_dev);
^
scripts/Makefile.build:308: recipe for target '~/fbtft/src/fbtft-git/fbtft-core.o' failed
make[1]: *** [~/fbtft/src/fbtft-git/fbtft-core.o] Error 1
Makefile:1224: recipe for target '_module_~/fbtft/src/fbtft-git' failed
make: *** [_module_~/fbtft/src/fbtft-git] Error 2
make: Leaving directory '/usr/src/linux-3.10.38-1-ARCH'
==> ERROR: A failure occurred in build().
Aborting...
')

[WarheadsSE]

Immediate thought: start grepping /usr/src for the definition of 'struct fb_info' on both platforms, and find the difference.

[dreamlocked]

Thank you for the reply. I grepped for 'struct fb_info' on both source directories and the result of diff on the sorted lists gives the output below.
It would seem that on the relevant header fb.h, 'struct fb_info' is defined as static on arm rather than extern which is the case on i686.
I will change the fb.h on the pi to be similar to the one on i686 when I get a chance and see what it gives.

The diff output:
$this->bbcode_second_pass_code('', '
$ diff armv6h_grep_list_sorted i686_grep_list_sorted

< ./arch/arm/include/asm/fb.h:static inline int fb_is_primary_device(struct fb_info *info)
---
> ./arch/x86/include/asm/fb.h:extern int fb_is_primary_device(struct fb_info *info);
110d109
< ./include/video/atmel_lcdc.h: struct fb_info *info;
')

ARMV6H: Detailed output of grep -r 'struct fb_info' ./* | sort
$this->bbcode_second_pass_code('', '
./arch/arm/include/asm/fb.h:static inline int fb_is_primary_device(struct fb_info *info)
./include/asm-generic/fb.h:static inline int fb_is_primary_device(struct fb_info *info)
./include/drm/drm_fb_helper.h: struct fb_info *info);
./include/drm/drm_fb_helper.h: struct fb_info *info);
./include/drm/drm_fb_helper.h: struct fb_info *fbdev;
./include/drm/drm_fb_helper.h:int drm_fb_helper_blank(int blank, struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_debug_enter(struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_debug_leave(struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_set_par(struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info);
./include/drm/drm_fb_helper.h:void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
./include/drm/drm_fb_helper.h:void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helper,
./include/linux/amba/clcd.h: struct fb_info fb;
./include/linux/backlight.h: int (*check_fb)(struct backlight_device *, struct fb_info *);
./include/linux/backlight.h:struct fb_info;
./include/linux/fb.h: struct fb_info *info);
./include/linux/fb.h: unsigned blue, unsigned transp, struct fb_info *info);
./include/linux/fb.h: struct fb_info *info, const char *mode_option,
./include/linux/fb.h: struct fb_info *info);
./include/linux/fb.h: int (*fb_blank)(int blank, struct fb_info *info);
./include/linux/fb.h: int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);
./include/linux/fb.h: int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
./include/linux/fb.h: int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);
./include/linux/fb.h: int (*fb_debug_enter)(struct fb_info *info);
./include/linux/fb.h: int (*fb_debug_leave)(struct fb_info *info);
./include/linux/fb.h: int (*fb_get_tilemax)(struct fb_info *info);
./include/linux/fb.h: int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
./include/linux/fb.h: int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);
./include/linux/fb.h: int (*fb_open)(struct fb_info *info, int user);
./include/linux/fb.h: int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
./include/linux/fb.h: int (*fb_release)(struct fb_info *info, int user);
./include/linux/fb.h: int (*fb_set_par)(struct fb_info *info);
./include/linux/fb.h: int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);
./include/linux/fb.h: int (*fb_sync)(struct fb_info *info);
./include/linux/fb.h: ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
./include/linux/fb.h: ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
./include/linux/fb.h: struct fb_info *info;
./include/linux/fb.h: void (*deferred_io)(struct fb_info *info, struct list_head *pagelist);
./include/linux/fb.h: void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
./include/linux/fb.h: void (*fb_destroy)(struct fb_info *info);
./include/linux/fb.h: void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
./include/linux/fb.h: void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
./include/linux/fb.h: void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);
./include/linux/fb.h: void (*fb_rotate)(struct fb_info *info, int angle);
./include/linux/fb.h: void (*fb_settile)(struct fb_info *info, struct fb_tilemap *map);
./include/linux/fb.h: void (*fb_tileblit)(struct fb_info *info, struct fb_tileblit *blit);
./include/linux/fb.h: void (*fb_tilecopy)(struct fb_info *info, struct fb_tilearea *area);
./include/linux/fb.h: void (*fb_tilecursor)(struct fb_info *info,
./include/linux/fb.h: void (*fb_tilefill)(struct fb_info *info, struct fb_tilerect *rect);
./include/linux/fb.h: void (*first_io)(struct fb_info *info);
./include/linux/fb.h: void (*readio) (struct fb_info *info, void *dst, void __iomem *src, unsigned int size);
./include/linux/fb.h: void (*writeio)(struct fb_info *info, void __iomem *dst, void *src, unsigned int size);
./include/linux/fb.h:extern char* fb_get_buffer_offset(struct fb_info *info, struct fb_pixmap *buf, u32 size);
./include/linux/fb.h:extern int fb_blank(struct fb_info *info, int blank);
./include/linux/fb.h:extern int fb_init_device(struct fb_info *fb_info);
./include/linux/fb.h:extern int fb_new_modelist(struct fb_info *info);
./include/linux/fb.h:extern int fb_pan_display(struct fb_info *info, struct fb_var_screeninfo *var);
./include/linux/fb.h:extern int fb_prepare_logo(struct fb_info *fb_info, int rotate);
./include/linux/fb.h:extern int fb_set_cmap(struct fb_cmap *cmap, struct fb_info *fb_info);
./include/linux/fb.h:extern int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *fb_info);
./include/linux/fb.h:extern int fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var);
./include/linux/fb.h:extern int fb_show_logo(struct fb_info *fb_info, int rotate);
./include/linux/fb.h:extern int fbmon_dpms(const struct fb_info *fb_info);
./include/linux/fb.h:extern int lock_fb_info(struct fb_info *info);
./include/linux/fb.h:extern int register_framebuffer(struct fb_info *fb_info);
./include/linux/fb.h:extern int unlink_framebuffer(struct fb_info *fb_info);
./include/linux/fb.h:extern int unregister_framebuffer(struct fb_info *fb_info);
./include/linux/fb.h:extern ssize_t fb_sys_read(struct fb_info *info, char __user *buf,
./include/linux/fb.h:extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
./include/linux/fb.h:extern struct fb_info *framebuffer_alloc(size_t size, struct device *dev);
./include/linux/fb.h:extern struct fb_info *registered_fb[FB_MAX];
./include/linux/fb.h:extern void cfb_copyarea(struct fb_info *info, const struct fb_copyarea *area);
./include/linux/fb.h:extern void cfb_fillrect(struct fb_info *info, const struct fb_fillrect *rect);
./include/linux/fb.h:extern void cfb_imageblit(struct fb_info *info, const struct fb_image *image);
./include/linux/fb.h:extern void fb_bl_default_curve(struct fb_info *fb_info, u8 off, u8 min, u8 max);
./include/linux/fb.h:extern void fb_cleanup_device(struct fb_info *head);
./include/linux/fb.h:extern void fb_deferred_io_cleanup(struct fb_info *info);
./include/linux/fb.h:extern void fb_deferred_io_init(struct fb_info *info);
./include/linux/fb.h:extern void fb_deferred_io_open(struct fb_info *info,
./include/linux/fb.h:extern void fb_set_suspend(struct fb_info *info, int state);
./include/linux/fb.h:extern void framebuffer_release(struct fb_info *info);
./include/linux/fb.h:extern void sys_copyarea(struct fb_info *info, const struct fb_copyarea *area);
./include/linux/fb.h:extern void sys_fillrect(struct fb_info *info, const struct fb_fillrect *rect);
./include/linux/fb.h:extern void sys_imageblit(struct fb_info *info, const struct fb_image *image);
./include/linux/fb.h:static inline bool fb_be_math(struct fb_info *info)
./include/linux/fb.h:static inline void unlock_fb_info(struct fb_info *info)
./include/linux/fb.h:struct fb_info {
./include/linux/fb.h:struct fb_info;
./include/linux/lcd.h: int (*check_fb)(struct lcd_device *, struct fb_info *);
./include/linux/lcd.h:struct fb_info;
./include/linux/platform_data/video-ep93xx.h: void (*blank)(int blank_mode, struct fb_info *info);
./include/linux/platform_data/video-ep93xx.h:struct fb_info;
./include/linux/platform_data/video-msm_fb.h: int (*blit)(struct mdp_device *mdp, struct fb_info *fb,
./include/linux/platform_data/video-msm_fb.h:struct fb_info;
./include/linux/platform_data/video-pxafb.h: void (*smart_update)(struct fb_info *);
./include/linux/platform_data/video-pxafb.h:extern int pxafb_smart_flush(struct fb_info *info);
./include/linux/platform_data/video-pxafb.h:extern int pxafb_smart_queue(struct fb_info *info, uint16_t *cmds, int);
./include/linux/platform_data/video-pxafb.h:static inline int pxafb_smart_flush(struct fb_info *info)
./include/linux/platform_data/video-pxafb.h:static inline int pxafb_smart_queue(struct fb_info *info,
./include/linux/pwm_backlight.h: int (*check_fb)(struct device *dev, struct fb_info *info);
./include/linux/svga.h:int svga_get_tilemax(struct fb_info *info);
./include/linux/svga.h:void svga_get_caps(struct fb_info *info, struct fb_blit_caps *caps,
./include/linux/svga.h:void svga_settile(struct fb_info *info, struct fb_tilemap *map);
./include/linux/svga.h:void svga_tileblit(struct fb_info *info, struct fb_tileblit *blit);
./include/linux/svga.h:void svga_tilecopy(struct fb_info *info, struct fb_tilearea *area);
./include/linux/svga.h:void svga_tilecursor(void __iomem *regbase, struct fb_info *info, struct fb_tilecursor *cursor);
./include/linux/svga.h:void svga_tilefill(struct fb_info *info, struct fb_tilerect *rect);
./include/linux/vga_switcheroo.h: struct fb_info *info);
./include/linux/vga_switcheroo.h:static inline void vga_switcheroo_client_fb_set(struct pci_dev *dev, struct fb_info *info) {}
./include/video/atmel_lcdc.h: struct fb_info *info;
./include/video/auo_k190xfb.h: int (*setup_irq)(struct fb_info *);
./include/video/auo_k190xfb.h: struct fb_info *info;
./include/video/broadsheetfb.h: int (*setup_irq)(struct fb_info *);
./include/video/broadsheetfb.h: struct fb_info *info;
./include/video/exynos_mipi_dsim.h: int (*get_fb_frame_done)(struct fb_info *info);
./include/video/exynos_mipi_dsim.h: void (*trigger)(struct fb_info *info);
./include/video/hecubafb.h: struct fb_info *info;
./include/video/mbxfb.h: int (*probe)(struct fb_info *fb);
./include/video/mbxfb.h: int (*remove)(struct fb_info *fb);
./include/video/mbxfb.h:struct fb_info;
./include/video/metronomefb.h: int (*setup_irq)(struct fb_info *);
./include/video/metronomefb.h: struct fb_info *host_fbinfo; /* the host LCD controller's fbi */
./include/video/metronomefb.h: struct fb_info *info;
./include/video/platform_lcd.h: int (*match_fb)(struct plat_lcd_data *, struct fb_info *);
./include/video/platform_lcd.h:struct fb_info;
./include/video/pxa168fb.h: struct fb_info *info;
./include/video/sstfb.h: int (*detect) (struct fb_info *info);
./include/video/sstfb.h: int (*set_pll) (struct fb_info *info, const struct pll_timing *t, const int clock);
./include/video/sstfb.h: void (*set_vidmod) (struct fb_info *info, const int bpp);
./include/video/udlfb.h: struct fb_info *info;
')

i686: Detailed output of grep -r 'struct fb_info' ./* | sort
$this->bbcode_second_pass_code('', '
./arch/x86/include/asm/fb.h:extern int fb_is_primary_device(struct fb_info *info);
./include/asm-generic/fb.h:static inline int fb_is_primary_device(struct fb_info *info)
./include/drm/drm_fb_helper.h: struct fb_info *info);
./include/drm/drm_fb_helper.h: struct fb_info *info);
./include/drm/drm_fb_helper.h: struct fb_info *fbdev;
./include/drm/drm_fb_helper.h:int drm_fb_helper_blank(int blank, struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_debug_enter(struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_debug_leave(struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_set_par(struct fb_info *info);
./include/drm/drm_fb_helper.h:int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info);
./include/drm/drm_fb_helper.h:void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
./include/drm/drm_fb_helper.h:void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helper,
./include/linux/amba/clcd.h: struct fb_info fb;
./include/linux/backlight.h: int (*check_fb)(struct backlight_device *, struct fb_info *);
./include/linux/backlight.h:struct fb_info;
./include/linux/fb.h: struct fb_info *info);
./include/linux/fb.h: unsigned blue, unsigned transp, struct fb_info *info);
./include/linux/fb.h: struct fb_info *info, const char *mode_option,
./include/linux/fb.h: struct fb_info *info);
./include/linux/fb.h: int (*fb_blank)(int blank, struct fb_info *info);
./include/linux/fb.h: int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);
./include/linux/fb.h: int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
./include/linux/fb.h: int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);
./include/linux/fb.h: int (*fb_debug_enter)(struct fb_info *info);
./include/linux/fb.h: int (*fb_debug_leave)(struct fb_info *info);
./include/linux/fb.h: int (*fb_get_tilemax)(struct fb_info *info);
./include/linux/fb.h: int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
./include/linux/fb.h: int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);
./include/linux/fb.h: int (*fb_open)(struct fb_info *info, int user);
./include/linux/fb.h: int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
./include/linux/fb.h: int (*fb_release)(struct fb_info *info, int user);
./include/linux/fb.h: int (*fb_set_par)(struct fb_info *info);
./include/linux/fb.h: int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);
./include/linux/fb.h: int (*fb_sync)(struct fb_info *info);
./include/linux/fb.h: ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
./include/linux/fb.h: ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
./include/linux/fb.h: struct fb_info *info;
./include/linux/fb.h: void (*deferred_io)(struct fb_info *info, struct list_head *pagelist);
./include/linux/fb.h: void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
./include/linux/fb.h: void (*fb_destroy)(struct fb_info *info);
./include/linux/fb.h: void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
./include/linux/fb.h: void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
./include/linux/fb.h: void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);
./include/linux/fb.h: void (*fb_rotate)(struct fb_info *info, int angle);
./include/linux/fb.h: void (*fb_settile)(struct fb_info *info, struct fb_tilemap *map);
./include/linux/fb.h: void (*fb_tileblit)(struct fb_info *info, struct fb_tileblit *blit);
./include/linux/fb.h: void (*fb_tilecopy)(struct fb_info *info, struct fb_tilearea *area);
./include/linux/fb.h: void (*fb_tilecursor)(struct fb_info *info,
./include/linux/fb.h: void (*fb_tilefill)(struct fb_info *info, struct fb_tilerect *rect);
./include/linux/fb.h: void (*first_io)(struct fb_info *info);
./include/linux/fb.h: void (*readio) (struct fb_info *info, void *dst, void __iomem *src, unsigned int size);
./include/linux/fb.h: void (*writeio)(struct fb_info *info, void __iomem *dst, void *src, unsigned int size);
./include/linux/fb.h:extern char* fb_get_buffer_offset(struct fb_info *info, struct fb_pixmap *buf, u32 size);
./include/linux/fb.h:extern int fb_blank(struct fb_info *info, int blank);
./include/linux/fb.h:extern int fb_init_device(struct fb_info *fb_info);
./include/linux/fb.h:extern int fb_new_modelist(struct fb_info *info);
./include/linux/fb.h:extern int fb_pan_display(struct fb_info *info, struct fb_var_screeninfo *var);
./include/linux/fb.h:extern int fb_prepare_logo(struct fb_info *fb_info, int rotate);
./include/linux/fb.h:extern int fb_set_cmap(struct fb_cmap *cmap, struct fb_info *fb_info);
./include/linux/fb.h:extern int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *fb_info);
./include/linux/fb.h:extern int fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var);
./include/linux/fb.h:extern int fb_show_logo(struct fb_info *fb_info, int rotate);
./include/linux/fb.h:extern int fbmon_dpms(const struct fb_info *fb_info);
./include/linux/fb.h:extern int lock_fb_info(struct fb_info *info);
./include/linux/fb.h:extern int register_framebuffer(struct fb_info *fb_info);
./include/linux/fb.h:extern int unlink_framebuffer(struct fb_info *fb_info);
./include/linux/fb.h:extern int unregister_framebuffer(struct fb_info *fb_info);
./include/linux/fb.h:extern ssize_t fb_sys_read(struct fb_info *info, char __user *buf,
./include/linux/fb.h:extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
./include/linux/fb.h:extern struct fb_info *framebuffer_alloc(size_t size, struct device *dev);
./include/linux/fb.h:extern struct fb_info *registered_fb[FB_MAX];
./include/linux/fb.h:extern void cfb_copyarea(struct fb_info *info, const struct fb_copyarea *area);
./include/linux/fb.h:extern void cfb_fillrect(struct fb_info *info, const struct fb_fillrect *rect);
./include/linux/fb.h:extern void cfb_imageblit(struct fb_info *info, const struct fb_image *image);
./include/linux/fb.h:extern void fb_bl_default_curve(struct fb_info *fb_info, u8 off, u8 min, u8 max);
./include/linux/fb.h:extern void fb_cleanup_device(struct fb_info *head);
./include/linux/fb.h:extern void fb_deferred_io_cleanup(struct fb_info *info);
./include/linux/fb.h:extern void fb_deferred_io_init(struct fb_info *info);
./include/linux/fb.h:extern void fb_deferred_io_open(struct fb_info *info,
./include/linux/fb.h:extern void fb_set_suspend(struct fb_info *info, int state);
./include/linux/fb.h:extern void framebuffer_release(struct fb_info *info);
./include/linux/fb.h:extern void sys_copyarea(struct fb_info *info, const struct fb_copyarea *area);
./include/linux/fb.h:extern void sys_fillrect(struct fb_info *info, const struct fb_fillrect *rect);
./include/linux/fb.h:extern void sys_imageblit(struct fb_info *info, const struct fb_image *image);
./include/linux/fb.h:static inline bool fb_be_math(struct fb_info *info)
./include/linux/fb.h:static inline void unlock_fb_info(struct fb_info *info)
./include/linux/fb.h:struct fb_info {
./include/linux/fb.h:struct fb_info;
./include/linux/lcd.h: int (*check_fb)(struct lcd_device *, struct fb_info *);
./include/linux/lcd.h:struct fb_info;
./include/linux/platform_data/video-ep93xx.h: void (*blank)(int blank_mode, struct fb_info *info);
./include/linux/platform_data/video-ep93xx.h:struct fb_info;
./include/linux/platform_data/video-msm_fb.h: int (*blit)(struct mdp_device *mdp, struct fb_info *fb,
./include/linux/platform_data/video-msm_fb.h:struct fb_info;
./include/linux/platform_data/video-pxafb.h: void (*smart_update)(struct fb_info *);
./include/linux/platform_data/video-pxafb.h:extern int pxafb_smart_flush(struct fb_info *info);
./include/linux/platform_data/video-pxafb.h:extern int pxafb_smart_queue(struct fb_info *info, uint16_t *cmds, int);
./include/linux/platform_data/video-pxafb.h:static inline int pxafb_smart_flush(struct fb_info *info)
./include/linux/platform_data/video-pxafb.h:static inline int pxafb_smart_queue(struct fb_info *info,
./include/linux/pwm_backlight.h: int (*check_fb)(struct device *dev, struct fb_info *info);
./include/linux/svga.h:int svga_get_tilemax(struct fb_info *info);
./include/linux/svga.h:void svga_get_caps(struct fb_info *info, struct fb_blit_caps *caps,
./include/linux/svga.h:void svga_settile(struct fb_info *info, struct fb_tilemap *map);
./include/linux/svga.h:void svga_tileblit(struct fb_info *info, struct fb_tileblit *blit);
./include/linux/svga.h:void svga_tilecopy(struct fb_info *info, struct fb_tilearea *area);
./include/linux/svga.h:void svga_tilecursor(void __iomem *regbase, struct fb_info *info, struct fb_tilecursor *cursor);
./include/linux/svga.h:void svga_tilefill(struct fb_info *info, struct fb_tilerect *rect);
./include/linux/vga_switcheroo.h: struct fb_info *info);
./include/linux/vga_switcheroo.h:static inline void vga_switcheroo_client_fb_set(struct pci_dev *dev, struct fb_info *info) {}
./include/video/auo_k190xfb.h: int (*setup_irq)(struct fb_info *);
./include/video/auo_k190xfb.h: struct fb_info *info;
./include/video/broadsheetfb.h: int (*setup_irq)(struct fb_info *);
./include/video/broadsheetfb.h: struct fb_info *info;
./include/video/exynos_mipi_dsim.h: int (*get_fb_frame_done)(struct fb_info *info);
./include/video/exynos_mipi_dsim.h: void (*trigger)(struct fb_info *info);
./include/video/hecubafb.h: struct fb_info *info;
./include/video/mbxfb.h: int (*probe)(struct fb_info *fb);
./include/video/mbxfb.h: int (*remove)(struct fb_info *fb);
./include/video/mbxfb.h:struct fb_info;
./include/video/metronomefb.h: int (*setup_irq)(struct fb_info *);
./include/video/metronomefb.h: struct fb_info *host_fbinfo; /* the host LCD controller's fbi */
./include/video/metronomefb.h: struct fb_info *info;
./include/video/platform_lcd.h: int (*match_fb)(struct plat_lcd_data *, struct fb_info *);
./include/video/platform_lcd.h:struct fb_info;
./include/video/pxa168fb.h: struct fb_info *info;
./include/video/sstfb.h: int (*detect) (struct fb_info *info);
./include/video/sstfb.h: int (*set_pll) (struct fb_info *info, const struct pll_timing *t, const int clock);
./include/video/sstfb.h: void (*set_vidmod) (struct fb_info *info, const int bpp);
./include/video/udlfb.h: struct fb_info *info;
')

[dreamlocked]

Unfortunately, editing the /arch/arm/include/asm/fb.h file did not alter the build error.
Must be something else.

[WarheadsSE]

No... that function was defined differently, that is not the struct itself.

[dreamlocked]

Ok, I think I found what's wrong. The kernel module fb_backlight is not set.

On i686
$this->bbcode_second_pass_code('', '
$ grep -r CONFIG_FB_BACKLIGHT ./*

include/uapi/linux/fb.h:#ifdef CONFIG_FB_BACKLIGHT
include/config/auto.conf:CONFIG_FB_BACKLIGHT=y
include/generated/autoconf.h:#define CONFIG_FB_BACKLIGHT 1
include/linux/fb.h:#ifdef CONFIG_FB_BACKLIGHT
.config:CONFIG_FB_BACKLIGHT=y
')

On armv6h
$this->bbcode_second_pass_code('', '
$ grep -r CONFIG_FB_BACKLIGHT

.config:# CONFIG_FB_BACKLIGHT is not set
include/uapi/linux/fb.h:#ifdef CONFIG_FB_BACKLIGHT
include/linux/fb.h:#ifdef CONFIG_FB_BACKLIGHT
')

This would probably explain the errors complaining about 'bl_dev'. Indeed, CONFIG_FB_BACKLIGHT is required for it to be defined.
In include/linux/fb.h:
$this->bbcode_second_pass_code('', '
#ifdef CONFIG_FB_BACKLIGHT
/* assigned backlight device */
/* set before framebuffer registration,
remove after unregister */
struct backlight_device *bl_dev;

/* Backlight level curve */
struct mutex bl_curve_mutex;
u8 bl_curve[FB_BACKLIGHT_LEVELS];
#endif
')

Thanks again for pointing in the right direction.