Re: [PATCH 1/2] lib/vsprintf: Add support for generic FourCCs by extending %p4cc

[Aditya Garg]

> On 13 Mar 2025, at 2:19 PM, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> 
> On Thu, Mar 13, 2025 at 07:26:05AM +0000, Aditya Garg wrote:
>>>> On 13 Mar 2025, at 12:58 AM, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>>> On Wed, Mar 12, 2025 at 07:14:36PM +0000, Aditya Garg wrote:
>>>>> On 12 Mar 2025, at 9:05 PM, Sven Peter <sven@xxxxxxxxxxxxx> wrote:
>>>>> On Wed, Mar 12, 2025, at 13:03, Aditya Garg wrote:
> 
> ...
> 
>>>>> I don't have a strong opinion either way: for SMC I just need to print
>>>>> FourCC keys for debugging / information in a few places.
>>>>> 
>>>>> I'm preparing the SMC driver for upstreaming again (after a two year delay :-()
>>>>> and was just going to use macros to print the SMC FourCC keys similar to
>>>>> DRM_MODE_FMT/DRM_MODE_ARG for now to keep the series smaller and revisit
>>>>> the topic later.
>>>>> 
>>>>> Right now I have these in my local tree (only compile tested so far):
>>>>> 
>>>>> #define SMC_KEY_FMT "%c%c%c%c (0x%08x)"
>>>>> #define SMC_KEY_ARG(k) (k)>>24, (k)>>16, (k)>>8, (k), (k)
>>>> 
>>>> That seems to be a nice alternative, which I guess Thomas was also suggesting.
>>> 
>>> I don't think it's "nice". Each of the approaches has pros and cons.
>>> You can start from bloat-o-meter here and compare it with your %p extension.
>>> 
>>> Also, can you show the bloat-o-meter output for the vsprintf.c?
>> 
>> Here are your outputs:
> 
> Thank you!
> 
>> ---------------------------------------------------------------------
>> For appletbdrm:
>> 
>> aditya@MacBook:~/linux$ ./scripts/bloat-o-meter $P4 $MACRO
>> add/remove: 0/0 grow/shrink: 1/1 up/down: 64/-19 (45)
>> Function                                     old     new   delta
>> appletbdrm_read_response                     395     459     +64
>> appletbdrm_probe                            1786    1767     -19
>> Total: Before=13418, After=13463, chg +0.34%
> 
> This is enough, no need to repeat this for every parameter.
> 
>> ---------------------------------------------------------------------
>> For vsprintf:
>> 
>> aditya@MacBook:~/linux$ ./scripts/bloat-o-meter $OLD $NEW
>> add/remove: 0/0 grow/shrink: 1/0 up/down: 220/0 (220)
>> Function                                     old     new   delta
>> fourcc_string                                479     699    +220
>> Total: Before=26454, After=26674, chg +0.83%
> 
> So, we get +220 bytes vs +43 bytes. It means if we found 5+ users, it worth
> doing.
> 

Will it also depend upon the number of times it's being used? In appletbdrm, it is being used 3 times. Probably more in Asahi SMC.
>>>>> which are then used like this:
>>>>> 
>>>>> dev_info(dev,
>>>>>     "Initialized (%d keys " SMC_KEY_FMT " .. " SMC_KEY_FMT ")\n",
>>>>>      smc->key_count, SMC_KEY_ARG(smc->first_key),
>>>>>      SMC_KEY_ARG(smc->last_key));
> 
> --
> With Best Regards,
> Andy Shevchenko
> 
>