In sm750fb_setup and sm750fb_set_drv functions, the dualview
related code is guarded by `sm750_dev->fb_count > 1` condition.
That value is updated only after each framebuffer is registered,
while both guards are used before any increment.

Current flow:

  lynxfb_pci_probe()
    sm750fb_setup()                 // fb_count is 0
    for each fb:
      sm750fb_framebuffer_alloc()
        lynxfb_set_fbinfo()
          sm750fb_set_drv()         // fb_count is 0 or 1
        register_framebuffer()
        sm750_dev->fb_count++;      // fb_count is incremented

Thus even if `dualview=1` parameter is passed down to the driver,
fb_count is never > 1 at either check, so dualview dataflows are
not selected and crtc->vidmem_size is never halved.

Use `g_dualview` global variable instead of fb_count > 1 to correctly
enable dualview capabilities.

Fixes: a3f92cc94c61 ("staging: sm750fb: replace dual member of sm750_dev with fb_count")
Signed-off-by: Ahmet Sezgin Duran <ahmet@sezginduran.net>
---
Found by code inspection. Not tested on sm750 hardware. This restores
the gate that selects the dual-display dataflow but does not validate
the rest of that path, which has been unreachable since commit a3f92cc94c61.

 drivers/staging/sm750fb/sm750.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750.c b/drivers/staging/sm750fb/sm750.c
index 89c811e0806c..3a4b9c06f770 100644
--- a/drivers/staging/sm750fb/sm750.c
+++ b/drivers/staging/sm750fb/sm750.c
@@ -591,7 +591,7 @@ static int sm750fb_set_drv(struct lynxfb_par *par)
 	crtc = &par->crtc;
 
 	crtc->vidmem_size = sm750_dev->vidmem_size;
-	if (sm750_dev->fb_count > 1)
+	if (g_dualview)
 		crtc->vidmem_size >>= 1;
 
 	/* setup crtc and output member */
@@ -896,7 +896,7 @@ static void sm750fb_setup(struct sm750_dev *sm750_dev, char *src)
 
 NO_PARAM:
 	if (sm750_dev->revid != SM750LE_REVISION_ID) {
-		if (sm750_dev->fb_count > 1) {
+		if (g_dualview) {
 			if (swap)
 				sm750_dev->dataflow = sm750_dual_swap;
 			else
-- 
2.53.0