linux-kernel - Re: [PATCH v2 1/2] dma-buf: heaps: system: Remove global variable

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Message-ID: <e268d75d-c75a-499e-872d-09f91defed6b@amd.com>
Date: Tue, 1 Apr 2025 17:28:43 +0200
From: Christian König <christian.koenig@....com>
To: Maxime Ripard <mripard@...nel.org>, Rob Herring <robh@...nel.org>,
 Saravana Kannan <saravanak@...gle.com>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
 "T.J. Mercier" <tjmercier@...gle.com>
Cc: Mattijs Korpershoek <mkorpershoek@...nel.org>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v2 1/2] dma-buf: heaps: system: Remove global variable

Am 01.04.25 um 17:12 schrieb Maxime Ripard:
> The system heap has been using its struct dma_heap pointer but wasn't
> using it anywhere.
>
> Since we'll need additional parameters to attach to that heap type,
> let's create a private structure and set it as the dma_heap drvdata,
> removing the global variable in the process.
>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>  drivers/dma-buf/heaps/system_heap.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index 26d5dc89ea1663a0d078e3a5723ca3d8d12b935f..adf422eaa33a52794f952d9d4260b8743d37f421 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -19,11 +19,13 @@
>  #include <linux/module.h>
>  #include <linux/scatterlist.h>
>  #include <linux/slab.h>
>  #include <linux/vmalloc.h>
>  
> -static struct dma_heap *sys_heap;
> +struct system_heap {
> +	struct dma_heap *heap;
> +};
>  
>  struct system_heap_buffer {
>  	struct dma_heap *heap;
>  	struct list_head attachments;
>  	struct mutex lock;
> @@ -422,17 +424,22 @@ static const struct dma_heap_ops system_heap_ops = {
>  };
>  
>  static int __init system_heap_create(void)
>  {
>  	struct dma_heap_export_info exp_info;
> +	struct system_heap *sys_heap;
> +
> +	sys_heap = kzalloc(sizeof(*sys_heap), GFP_KERNEL);
> +	if (!sys_heap)
> +		return -ENOMEM;
>  
>  	exp_info.name = "system";
>  	exp_info.ops = &system_heap_ops;
> -	exp_info.priv = NULL;
> +	exp_info.priv = sys_heap;

Why do you even need this?

>  
> -	sys_heap = dma_heap_add(&exp_info);
> -	if (IS_ERR(sys_heap))
> -		return PTR_ERR(sys_heap);
> +	sys_heap->heap = dma_heap_add(&exp_info);
> +	if (IS_ERR(sys_heap->heap))
> +		return PTR_ERR(sys_heap->heap);

That's clearly missing freeing sys_heap again.

Christian.

>  
>  	return 0;
>  }
>  module_init(system_heap_create);
>