Am Sat, 7 Feb 2015 12:26:27 +0100
schrieb Maxime Ripard [off-list ref]:

On Fri, Feb 06, 2015 at 11:28:12PM +0100, niederp@physik.uni-kl.de
wrote:

quoted

From: Thomas Niederprüm <redacted>

This patch adds the module parameter "delaydivider" to set delay
for the deferred io. Effectively this is setting the refresh rate
for mmap access to the framebuffer. The delay for the deferred io
is HZ/delaydivider.

So this is actually a refresh rate?

Maybe you could expose it as such, and pass a frequency in Hz as an
argument.

Good idea! I'll try to do it that way.

Exposing the divider directly has some issues, since the bootloader
that set the parameter won't know the HZ value, you'll end up with
different rates for different configurations, without any way to do
something about it.

quoted

Signed-off-by: Thomas Niederprüm <redacted>
---
 drivers/video/fbdev/ssd1307fb.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c

b/drivers/video/fbdev/ssd1307fb.c index 1d81877..b38315d 100644

--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c

@@ -44,10 +44,14 @@
 #define	SSD1307FB_SET_VCOMH		0xdb
 
 #define BITSPERPIXEL 1
+#define DELAYDIVIDER 20
 
 static u_int bitsperpixel = BITSPERPIXEL;
 module_param(bitsperpixel, uint, 0);
 
+static u_int delaydivider = DELAYDIVIDER;
+module_param(delaydivider, uint, 0);
+

You're breaking the existing behaviour.

True! I'll try to keep the existing behaviour when rewriting this to
use the refresh rate.

quoted

 struct ssd1307fb_par;
 
 struct ssd1307fb_deviceinfo {

@@ -312,7 +316,7 @@ static void ssd1307fb_deferred_io(struct

fb_info *info, }
 
 static struct fb_deferred_io ssd1307fb_defio = {
-	.delay		= HZ,
+	.delay		= HZ/DELAYDIVIDER,
 	.deferred_io	= ssd1307fb_deferred_io,
 };
 

@@ -601,6 +605,7 @@ static int ssd1307fb_probe(struct i2c_client

*client, info->fix = ssd1307fb_fix;
 	info->fix.line_length = par->width * bitsperpixel / 8;
 	info->fbdefio = &ssd1307fb_defio;
+	info->fbdefio->delay = HZ/delaydivider;

That won't work with multiple instances of the same driver
unfortunately.

Could you please elaborate why? I'm not seeing it...

quoted

 
 	info->var = ssd1307fb_var;
 	info->var.bits_per_pixel = bitsperpixel;
-- 
2.1.1