[PATCH 1/6] amdgpu/dc: convert dc_transfer to use a kref.

[Christian König]

Am 03.10.2017 um 04:38 schrieb Dave Airlie:
> From: Dave Airlie <airlied at redhat.com>
>
> Rolling your own atomic ref counts is frowned upon.
>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
>   drivers/gpu/drm/amd/display/dc/core/dc_surface.c | 17 +++++++++--------
>   drivers/gpu/drm/amd/display/dc/dc.h              |  2 +-
>   drivers/gpu/drm/amd/display/dc/os_types.h        |  2 ++
>   3 files changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_surface.c b/drivers/gpu/drm/amd/display/dc/core/dc_surface.c
> index ff07105..c2168df 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_surface.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_surface.c
> @@ -161,17 +161,18 @@ struct dc_gamma *dc_create_gamma()
>   
>   void dc_transfer_func_retain(struct dc_transfer_func *tf)
>   {
> -	ASSERT(atomic_read(&tf->ref_count) > 0);
> -	atomic_inc(&tf->ref_count);
> +	kref_get(&tf->refcount);
>   }
>   
> -void dc_transfer_func_release(struct dc_transfer_func *tf)
> +static void dc_transfer_func_free(struct kref *kref)
>   {
> -	ASSERT(atomic_read(&tf->ref_count) > 0);
> -	atomic_dec(&tf->ref_count);
> +	struct dc_transfer_func *tf = container_of(kref, struct dc_transfer_func, refcount);
> +	kfree(tf);

Minor style nit pick, but we should have a new line between declaration 
and code. Alternative I could also like with "kfree(container....)".

Not that I care to much, but I had to spend a good part of my time 
beating people at AMD to come up with good kernel coding style :)

Christian.

> +}
>   
> -	if (atomic_read(&tf->ref_count) == 0)
> -		kfree(tf);
> +void dc_transfer_func_release(struct dc_transfer_func *tf)
> +{
> +	kref_put(&tf->refcount, dc_transfer_func_free);
>   }
>   
>   struct dc_transfer_func *dc_create_transfer_func()
> @@ -181,7 +182,7 @@ struct dc_transfer_func *dc_create_transfer_func()
>   	if (tf == NULL)
>   		goto alloc_fail;
>   
> -	atomic_inc(&tf->ref_count);
> +	kref_init(&tf->refcount);
>   
>   	return tf;
>   
> diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
> index 9c0e000..17f0c73 100644
> --- a/drivers/gpu/drm/amd/display/dc/dc.h
> +++ b/drivers/gpu/drm/amd/display/dc/dc.h
> @@ -334,11 +334,11 @@ enum dc_transfer_func_predefined {
>   };
>   
>   struct dc_transfer_func {
> +	struct kref refcount;
>   	struct dc_transfer_func_distributed_points tf_pts;
>   	enum dc_transfer_func_type type;
>   	enum dc_transfer_func_predefined tf;
>   	struct dc_context *ctx;
> -	atomic_t ref_count;
>   };
>   
>   /*
> diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
> index 27ed2a6..e0cd527 100644
> --- a/drivers/gpu/drm/amd/display/dc/os_types.h
> +++ b/drivers/gpu/drm/amd/display/dc/os_types.h
> @@ -32,6 +32,8 @@
>   #include <linux/types.h>
>   #include <drm/drmP.h>
>   
> +#include <linux/kref.h>
> +
>   #include "cgs_linux.h"
>   
>   #if defined(__BIG_ENDIAN) && !defined(BIGENDIAN_CPU)