Re: [PATCH v3 06/15] drm/i915/display: add display platforms structure with platform members

[Jani Nikula <jani.nikula@intel.com>]

On Mon, 07 Oct 2024, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
> On Mon, Sep 30, 2024 at 03:31:07PM +0300, Jani Nikula wrote:
>> Add a structure with a bitfield member for each platform and
>> subplatform, and initialize them in platform and subplatform descs.
>> 
>> The structure also contains a bitmap in a union for easier manipulation
>> of the bits.
>> 
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  .../drm/i915/display/intel_display_device.c   |  4 ++++
>>  .../drm/i915/display/intel_display_device.h   | 19 +++++++++++++++++++
>>  2 files changed, 23 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_device.c b/drivers/gpu/drm/i915/display/intel_display_device.c
>> index b2610217f5c5..258660b49eba 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_device.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display_device.c
>> @@ -31,6 +31,7 @@ struct stepping_desc {
>>  	.step_info.size = ARRAY_SIZE(_map)
>>  
>>  struct subplatform_desc {
>> +	struct intel_display_platforms platforms;
>>  	enum intel_display_platform subplatform;
>>  	const char *name;
>>  	const u16 *pciidlist;
>> @@ -38,10 +39,12 @@ struct subplatform_desc {
>>  };
>>  
>>  #define SUBPLATFORM(_platform, _subplatform)				\
>> +	.platforms._platform##_##_subplatform = 1,			\
>>  	.subplatform = (INTEL_DISPLAY_##_platform##_##_subplatform),	\
>>  	.name = #_subplatform
>>  
>>  struct platform_desc {
>> +	struct intel_display_platforms platforms;
>>  	enum intel_display_platform platform;
>>  	const char *name;
>>  	const struct subplatform_desc *subplatforms;
>> @@ -50,6 +53,7 @@ struct platform_desc {
>>  };
>>  
>>  #define PLATFORM(_platform)			 \
>> +	.platforms._platform = 1,		 \
>>  	.platform = (INTEL_DISPLAY_##_platform), \
>>  	.name = #_platform
>>  
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_device.h b/drivers/gpu/drm/i915/display/intel_display_device.h
>> index c4208c34cc31..f166d4698949 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_device.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_device.h
>> @@ -6,6 +6,7 @@
>>  #ifndef __INTEL_DISPLAY_DEVICE_H__
>>  #define __INTEL_DISPLAY_DEVICE_H__
>>  
>> +#include <linux/bitops.h>
>>  #include <linux/types.h>
>>  
>>  #include "intel_display_conversion.h"
>> @@ -104,6 +105,24 @@ enum intel_display_platform {
>>  
>>  #undef __ENUM
>>  
>> +#define __MEMBER(name) unsigned long name:1;
>> +#define __COUNT(x) 1 +
>> +
>> +#define __NUM_PLATFORMS (INTEL_DISPLAY_PLATFORMS(__COUNT) 0)
>> +
>> +struct intel_display_platforms {
>> +	union {
>> +		struct {
>> +			INTEL_DISPLAY_PLATFORMS(__MEMBER);
>> +		};
>> +		DECLARE_BITMAP(bitmap, __NUM_PLATFORMS);
>> +	};
>> +};
>> +
>> +#undef __MEMBER
>> +#undef __COUNT
>
> why do we need the count here?
> I'm afraid I didn't fully followed this macro...

"1 +" gets substituted for each platform in INTEL_DISPLAY_PLATFORMS(),
resulting in the number of platforms, stored in __NUM_PLATFORMS.

We use that for the DECLARE_BITMAP() above. And we're using a bitmap to
avoid hand-rolling bitmap_or(). Yeah, it's a bit icky, but a) gets the
job done, b) should not need to be manually updated when the number of
platforms grows.

BR,
Jani.

>
>> +#undef __NUM_PLATFORMS
>> +
>>  #define DEV_INFO_DISPLAY_FOR_EACH_FLAG(func) \
>>  	/* Keep in alphabetical order */ \
>>  	func(cursor_needs_physical); \
>> -- 
>> 2.39.5
>> 

-- 
Jani Nikula, Intel