Re: [PATCH 2/3] video: fbdev: Check Standard Timing against DMT

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 05/12/14 21:47, David Ung wrote:
> 
>> On 03/12/14 23:49, David Ung wrote:
>>> Add the VESA Display Monitor Timing (DMT) table.
>>> During parsing of Standard Timings, it compare the 2 byte STD code
>>> with DMT to see what the VESA mode should be.  If there is no entry in
>>> the vesa_modes table or no match found, it fallsback to the GTF
>>> timings.
>>>
>>> Signed-off-by: David Ung <davidu@nvidia.com>
>>> ---
>>>  drivers/video/fbdev/core/fbmon.c  | 20 ++++++----
>>> drivers/video/fbdev/core/modedb.c | 84
>> +++++++++++++++++++++++++++++++++++++++
>>>  include/linux/fb.h                | 10 +++++
>>>  3 files changed, 107 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/video/fbdev/core/fbmon.c
>>> b/drivers/video/fbdev/core/fbmon.c
>>> index 5b0e313..aa1110a 100644
>>> --- a/drivers/video/fbdev/core/fbmon.c
>>> +++ b/drivers/video/fbdev/core/fbmon.c
>>> @@ -526,16 +526,22 @@ static int get_std_timing(unsigned char *block,
>> struct fb_videomode *mode,
>>>  	refresh = (block[1] & 0x3f) + 60;
>>>
>>>  	DPRINTK("      %dx%d@%dHz\n", xres, yres, refresh);
>>> -	for (i = 0; i < VESA_MODEDB_SIZE; i++) {
>>> -		if (vesa_modes[i].xres == xres &&
>>> -		    vesa_modes[i].yres == yres &&
>>> -		    vesa_modes[i].refresh == refresh) {
>>> -			*mode = vesa_modes[i];
>>> +	for (i = 0; i < DMT_SIZE; i++) {
>>> +		u32 std_2byte_code = block[0] << 8 | block[1];
>>> +
>>> +		if (std_2byte_code == dmt_modes[i].std_2byte_code) {
>>> +			if (!dmt_modes[i].mode)
>>> +				break;
>>> +			*mode = *dmt_modes[i].mode;
>>>  			mode->flag |= FB_MODE_IS_STANDARD;
>>> -			return 1;
>>> +			DPRINTK("        DMT id=%d\n",
>> dmt_modes[i].dmt_id);
>>> +			break;
>>>  		}
>>>  	}
>>> -	calc_mode_timings(xres, yres, refresh, mode);
>>> +
>>> +	if (i == DMT_SIZE || !dmt_modes[i].mode)
>>> +		calc_mode_timings(xres, yres, refresh, mode);
>>> +
>>>  	return 1;
>>>  }
>>
>> I think this could be made a bit cleaner.
>>
>> The xres/yres/refresh calculation in get_std_timing doesn't matter for the
>> DMT code above. So in get_std_timing() you could first do the search for the
>> DMT mode, and if found, return from the function. After that the code
>> would do the GTF calculation.
>>
> 
> Yes, I've deleted the xres/yres/refresh calculation.

Sorry it's taken a while for me to respond...

I mean that the whole 'switch (ratio)' and related code in the beginning
of the get_std_timing() are not needed for the DMT loop. All that could
be moved inside the 'if (i == DMT_SIZE || !dmt_modes[i].mode)' block.

Also, in my opinion the code would be more easily understandable with
something like:

for (dmt loop) {
	if (std_2byte_code matches)
		break;
}

if (i < DMT_SIZE && dmt_modes[i].mode) {
	// DMT mode found
} else {
	// calculate GTF
}

 Tomi



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