[PATCH 3/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

[Thomas Zimmermann]

Hi

Am 01.02.22 um 15:36 schrieb Javier Martinez Canillas:
> On 2/1/22 15:05, Geert Uytterhoeven wrote:
>> Hi Javier,
>>
>> On Tue, Feb 1, 2022 at 2:02 PM Javier Martinez Canillas
>> <javierm at redhat.com> wrote:
>>> On 2/1/22 10:33, Thomas Zimmermann wrote:
>>>>> +{
>>>>> +    u8 col_end = col_start + cols - 1;
>>>>> +    int ret;
>>>>> +
>>>>> +    if (col_start == ssd1307->col_start && col_end == ssd1307->col_end)
>>>>> +            return 0;
>>>>> +
>>>>> +    ret = ssd1307_write_cmd(ssd1307->client, SSD1307_SET_COL_RANGE);
>>>>> +    if (ret < 0)
>>>>> +            return ret;
>>>>> +
>>>>> +    ret = ssd1307_write_cmd(ssd1307->client, col_start);
>>>>> +    if (ret < 0)
>>>>> +            return ret;
>>>>> +
>>>>> +    ret = ssd1307_write_cmd(ssd1307->client, col_end);
>>>>> +    if (ret < 0)
>>>>> +            return ret;
>>>>
>>>> Can you write these cmds in one step, such as setting up an array and
>>>> sending it with ssd1307_write_array?
>>>
>>> I don't think so because the commands are different. But I'll check the
>>> ssd1306 datasheet again to confirma that's the case.
>>
>> IIRC, I tried that while working on the optimizations for ssd1307fb,
>> and it didn't work.
>>
> 
> That's what I would had expected by reading the datasheet. Thanks a
> lot for confirming my assumption.

Thanks to both of you. I was asking because I found the code to be 
repetitive and it's not clear that these 3 statements belong together.

I'd like to suggest to add a function

   ssd1307_write_cmds(client, len, const u8 *cmds)

that loops through cmds and sends the values one by one. A call would 
look like this:

   const u8 set_col_range[] = {
     SSD1307_SET_COL_RANGE,
     col_start,
     col_end
   };

   ssd1307_write_cmds(client, ARRAY_SIZE(set_col_range), set_col_range);

AND/OR

You could have functions that take a command with arguments; either as 
va_args or with one function per number of arguments. Or you could 
combine all these somehow.

Best regards
Thomas

>   
> 
> Best regards,

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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