Re: [PATCH v12 3/6] fbmon: add videomode helpers

On Thu, Nov 22, 2012 at 09:50:10AM +0100, Laurent Pinchart wrote:

Hi Sascha,

On Thursday 22 November 2012 07:20:00 Sascha Hauer wrote:

...

On Wed, Nov 21, 2012 at 11:02:44PM +0100, Laurent Pinchart wrote:

...

Hi Steffen,

...

• htotal = vm->hactive + vm->hfront_porch + vm->hback_porch +

•  vm->hsync_len;
  

• vtotal = vm->vactive + vm->vfront_porch + vm->vback_porch +

•  vm->vsync_len;
  

• fbmode->refresh = (vm->pixelclock * 1000) / (htotal * vtotal);

This will fail if vm->pixelclock >= ((1 << 32) / 1000). The easiest solution is probably to use 64-bit computation.

You have displays with a pixelclock > 4GHz?

vm->pixelclock is expressed in Hz. vm->pixelclock * 1000 will thus overflow if the clock frequency is >= ~4.3 MHz. I have displays with a clock frequency higher than that :-)

If vm->pixelclock is in Hz, then the * 1000 above is wrong.

Sascha